 Okay, good morning all of you, we will start our proceeding today. You all should have following things in mind. In all electronic systems, there are two signals which are always omnipresent. One of course is the signal which is your input signal, the other is the noise and it is the signal to noise ratio which decide whether you will get the signal as the output or the noise as the output, okay. And in particular low amplitude low frequency signals which are more like a hum as we call is more damaging to the performance because they can be passed in almost all systems, why did I say so? So when you keep talking very small volume, you are actually not creating noise, actually it creates more noise then you shout, okay. This is of course a fun part of it. Let us consider what we were doing last time, we will still go through few of these slides and start in earnest the course itself, okay. Why I want to show you further because this is my belief that many of you question us over the years that what is the purpose of all this? Of course for individual it may be varying differently, you know. For some people you are here because your parents ask you to appear in JEE and for good luck you came here, okay. For some you are expecting some 4 years to pass with on Moodai, Tech Fest, FTAF, Border NAM, somehow that 4 years pass or dual degree students, 5 year unfortunately for them, okay. So they are just waiting for that time period to be over. If it becomes T is equal to N immediately they will be very happy. But there may be 10% maybe little more I hope so, who are really interested in what we are teaching. So this course essentially is addressing more to those people who still believe that engineering is interesting and also useful in your career, okay. If you can increase this number to 90% someday I think it will be great success for you as well as for me, okay. Let us start. Analog design needs to consider handling of positive or negative, last we did last time we said so we just repeat from there. In case of analog and I will show you later biasing is very, very important. Linearity is essential I this one problem I will solve today or one explanations I will derive for you. We just now said noise, you know since both signal and noise will go through a system and if your noise is higher the system does not tolerate it and then it will pass more noise than the signal. We also want lower drifts. The word drift is something you are supposed to go on a particular course and you move from the course is called drift. So let us say power supply voltage has to be 1.5 volt and if it drifts to 1.4 or 1.6 you may have much more problem in at your hand when you saw the circuit performance. Similar there are many other parameters can drift temperature for example 25 degrees what we assume in all 27 degree we assume 300 degree Kelvin but in real life when circuit start functioning the heat there is a heat dissipation in device everywhere and the board itself will get heated and the temperature may rise to as much as 35 to 40 degrees I mean in worst case 100 degrees. So the performance of the circuit has very strong dependence on environment around and that is called drift problems. Of course in many cases there are two kinds of problems one get one is called systematic that is we can predict if this happen this is going to be a priori we know this is going to be take care this is going to happen ahead like this so okay I will take care initially itself when it starts I will take care but there is something which is non-systematic they are random they are random what can do it happens and it can happen any instant of time okay. So as I said drift is very important both systematic and random errors are very crucial for our designs in this course I should not keep saying word design because I teach a course on analog VLSI design so I keep that word in my mind in this course we are really not going to design we are actually going to do analysis how to design and not really design future in case you happen to come for master course here or elsewhere you can take that option course VLSI analog there will actually design that how much it is made and what sizing and how we do that but here I think we are doing more analysis the problem with most silicon chips are that in digital circuit what we do is let us say I want to make a micro processor what I do is most companies may have or at least be I may actually have blocks which are pre-designed pre-fabricated a pre-test range memory block register blocks these are called standard cells the new name for all this is IPs intellectual property so each can be designed and hold and no you won't tell it to pay me I'll give you kind of these IPs are not available in analog because analog is so much varying things for you will have to create huge number of IP millions of them just to keep and maybe one out of that will be okay so it is impossible to actually create IPs in analog so every chip or every system has to be designed okay that is why there is nothing shortcuts in analog and that is why you have to learn analog seriously because every case is different from the last time then there is a problem in all digital people are looking for 0.8 volt power supply battery 1.1 volts say you will want to reduce power mobile there is a 1 volt battery now they want to reduce to 0.8 maybe 0.6 latter because power dissipation is very crucial for us so what we are saying that if you do good for digital which is very good if you digital may still work on 0.6 or 0.8 but that is against the whole grain of goodness for analog but since you will always as I said earlier digital will analog will be part of digital will work on a bad tools and say oh design a great car but tools are you know age old ambassador car custom tooling him or a part but you want a Toyota Corolla to come out it is very difficult but that is what the whole challenge is about therefore analog circuits though we want but not very low power but there is an effort and that is the challenge that how do you reduce the power even in analog which is otherwise very difficult to get a good performance so these are the issues when we design a chip though these are not relevant for circuit analysis but just to give you where we are that is the aim we are looking at okay what do I think maybe my English is not correct in that what I say that it should be able to reject much of the noise so that the signal gets amplified but noise does not as much will give you some example that if I want to have a 2 stage amplifier 3 stage amplifier and if I pass through this the device itself will add to a noise from his own there is a input noise going now this two noises are now input to the next amp so it should be tolerant less tolerant it should stop that noise to go ahead this is what I meant if I am not clear in that that is what is that clear so I repeat the three parameters in our analogs are GM which is trans conductance output resistance very important for us and the noise which we as I say we define as input referred this is very interesting word input referred noise is seen at the output is that clear and we say no but you must specify at the input what is possible so there is something word will change from output to input and we will say it is input and then the finally and the most important parameter in our design or in our circuits is the bandwidth how much frequency response that is let us say I am an amplifier and I want to design an amplifier which will amplify the signal even if the signal frequency goes to say gigahertz but this statement is very cheap or simple oh why what is big about having an amplifier which can amplify up to a gigahertz no most amplifier will not go beyond 2 megahertz a lot of effort has to be done if I had to amplify a gigahertz so this is called frequency response and associated which I did not say it specifically and last time I did say something about it there is a gain bandwidth as the product which is relevant to us so if we increase bandwidth your gain will go down to a gigahertz you may have a unity gain 1 1 1 gain that means no gain kind of or even less than 1 so not the only solution where gain has to be remained that something I want gain of 20 100 200 and that gain I must attain other why amplify if the gain is not there this is in life as well if I put some 2 hours here I must get a good grade output has to be good this also is an issue which is interrelated so GM has something to do with bandwidth GM has something to do with the gain so we must now look at if I increase GM what will happen but if I increase GM what else will happen which may not allow me to increase the bandwidth or vice-versa that is the crucial analysis we like there are different kinds of noises in the system one is called thermal noise another call one upon F noise we may not look into details but just to give a figure which I do not know whether you can see from here the this is log noise plotted is called noise voltage versus frequency do you see here somewhere so initially at low frequencies 1 upon F noise dominant is that clear the figure 1 upon F noise and as the frequency increases it is the thermal noise which takes over thermal noise is essentially because of random motion of electrons and other things atomic system so yeah there is a possibility that some may dominate somewhere some may so this FC cutoff may be higher or lower in different devices different systems so there is an issue how to control noise and all analog circuits are worried about this noise at the end of the day for those forget that it is the trans conductance which if you change will correspond to change the noise itself because the expression shows noise square is proportional to GM square is that clear now so if I increase GM for gain and bandwidth some way my noise is also increasing is that issue now clear that my noise is what I am worried okay as I said this may not be the major issue for you this force but just to get an idea that we are worried about noise in all of our designs has to be clear this is the word called input referred noise VN IN square noise is always expressed as squares a square voltage because it is somewhere related to power and therefore it is always expressed in voltages so VN IN square is equal to VN OUT square divided by gain square this is called input referred noise the reason why we always refer if you see the expression you need not know anything these are all controllable input parameters and therefore what is the noise essentially will come will be decided from the transistors and the inputs what you are connecting therefore we always refer noises to the input side by dividing this kind of three steps okay just to for design something we need to work on higher VDD if possible or what we call bias current should be stabilized we should also look for for the words are we will come back these are very important word in our analog PM what does this PM mean so PM is called phase margin so in analog circuit you can think of phase margin not a great thing if you have a signal V is equal to V0 or VA e to the power something or sin omega t plus theta or plus pi or whatever it is and if the signal goes through the system this 5 changes to something else so let us say 5 2 then the margin on phase margin is 5 to – 5 1 because the phase has changed is that clear it is called phase margin so it is very important for us because phase margin means something has now changed not only in the frequency but also in the phase shifts have come and therefore very crucial in our design and they are somewhere related to what we call and we look into this transfer functions you are not done control code so far I think so maybe I will introduce to you what is pole and 0 if you are done that course then I will say pole 0 so this pole 0 will come to the expressions and you know what I am talking they may decide whether system will remain stable what do you mean by stable that if I change the frequency or signal thing the gain should be proportional otherwise if it changes then I have worries and that is called stability of the system in simple term one may say I am designing an amplifier and if it starts oscillating that means it becomes an oscillator it is an unstable system and this is very simple you can see from your future when we do that when I design a good oscillator it actually dance down and become some kind of a damping system it gives you gain and reduce gains with you also okay so when you are trying to get a good oscillator that self-sustained it does not sustain when I am making an amplifier it does not start oscillating so I want the constant gain constant signal and it is changing now so there is a design that when I am designing amplifier it should not oscillate and when I am designing you have said it should not done should not amplify huge and then done now so these are the two complementary or contradictory terms which is word goes into word stable stability if it is an amplified should they mean amplify if it is a oscillator it should remain oscillating to do this we say constant GM kind of circuits is better there are many methods we see if time permitting and the other issues are offsets as I already said the drifts can occur and how to take care of offsets okay the another issue which I thought you should know which may not be directly related to our course but for this lecture I may tell you there is another analog or analog come digital system which is becoming most important as far as the money part in the silicon industry which is called RS why it is called money spinner because all of you barring exception may be holding a mobile may be holding more than one mobile if I give you 2g now you want 3g when we 3g networking start you will have 4g you want everything on your mobile now mobile works at different ways one is called GSM the other is CDMA you will see that in your communication course which later so either of the system which you have a frequency range which is around 890 MHz and above 2 GHz these ranges are called radio efficiency and since signals your voice is still analog much of the inputs you will create are analog these tips are called our systems are called mixed signal there will be analog blocks and then be digital so the RF which we are now creating which is what we are really looking for nowadays this is something like a typical mobile system I can have a look at it okay this is my antenna this upper part is receiver the lower part is transmitter okay so we start with first part which you see here the low noise amplifier this is analog low noise amplifier why it is low noise because the signal which we received from antenna is very very deep last time I said the strength depends on how far you are away from the tower and many a times it is called fade out you will not even have the signal this is why you need to boost that is the first amplifier which we put is amplifier low noise amplifier the interest part in this is because it is an amplifier it will have a bandwidth issue there will be a filter has to be created which will reject the frequencies which are not required from the signal this is called image reject filters this is also analog block you may need another amplification at the after rejection of those frequencies because initial gains will be smaller the next game to be higher and these programmable gains the gains can be modified then we put another image reject filter because you have a bandwidth issue created and then we go to what we call mixers which are partially analog partially digital okay and then we put a filter then you have another IF amplifier this is called image we have created intermediate frequencies after mixer let us say we have gigahertz you may go to few megahertz hundreds of megahertz and we may sometimes we may have more than one mixer to get a lower frequency which is called base band 20 megahertz then you may have this is what I have shown you here this is another mixer another filter and your base bands this is called receiver part beyond this base band once I receive I will convert to digital and further processing everything will be on DSP and at the end if you really want to see some displays or something you may convert that digital data output to analog so two more blocks which I have not shown is a to D converters and finally V2A converters but basic processing measure will be done in this way so a trans receiver this is called trans receiver why transceiver is why transmitter and receiver if you are transmitting your base bands are here this is called orthogonal system shown here base band one and base band two okay two mixers then you mix to a adder which is also analog adder filter IF control single side band mixture these are two major amplifier which are again power amplifiers and a buffer which are essentially analog blocks the power amplifier must have sufficient power so that from the antenna I can transmit for a longer lengths so this is a typical cellophane structure is that clear we may be not interested beyond base band in this course because we are not looking for digital part we are looking only for analog part so we are so one can see all that time what I am talking about in analog I am looking for amplifier mixers may be one for mixer you actually require a frequency source which is called written frequency synthesizer are also called voltage controlled oscillators now this VCO is an analog block which is given to a mixer so you have how much what you are going to do actually in analog and amplifier different kinds different bandwidths different noises need oscillators okay for different frequencies synthesize means different frequencies can be created you need filters low pass high pass band pass band digit all kinds of filters okay these are essential blocks in analog no more what is ISDN anyone heard okay S stand for what D stand for these of course digital n is network integrated services digital network is ISDN which is our BSNL or MTNL allows you to have all four that is data transmission video transmission computer connection and TV all can be trans fax all can be or even earlier telex is used to call all services can be given on a single line by switches is called ISDN this is a network kind of circuits which ISDN will provide to you so again you can see there will be D2A converters pulse generator filters line drivers balancers refilters and tone detectors all these are basically analog blocks partly converted from D2A digital to analog and now you do processing on analog part okay so this is very is it ISDN is replaced already by what cable modem cable itself can do all the jobs wireless can do all the job LANs are come WLANs Wi-Fi Wi-Max but what is the problem with IS what was the good thing in ISDN because it was on your telephone line which in old days will not believe it your parents may tell to get a telephone in Mumbai as late as 80s was a nightmare to register and after 8 months 1 year 2 years depends on if you know someone or you do not you may get your line to getting an ISDN was for an institute was an achievement it is when I had to bomb the God ISDN a director was thanked that is what now we are changed so much you do not realize but there was a time and we actually worked on such four systems okay these are essentially circuits which are called frequency modulated transmitters and receivers and you can see there are this is shown intentionally bipolar because these are old circuits you require inductances to pass it and say resistances different sizes all this of course you can have a loudspeaker you can have microphones and this was our old system but basic even now has not changed because you cannot change the basic operation of an amplifier or anything so even if we are then much more work to simplify it or reduce the components the basic idea of analog circuit design is still same as 50 years ago we were doing like mobile WLAN GPS or examples of RF the tradeoff in a why RF design I am showing you for your sake in the case of digital I did not show you very much but I showed you that there is a there is a triangle of design or what we call tradeoffs what are the three things last time I showed you I said I do not know whether I have shown that figure if not I will again show you this is let us say power this is speed this is how we call area of the chip your transistor area so if I want to reduce power then I will reduce speed but I may actually increase or if I want same speed then I may increase the area so triangle has to be pulled up or pulled down but the wall net area will remain same in the technology you cannot achieve all goodness because of the triangle limitation but if you see RF this is the problem how many things we control there three and how many now I am controlling almost hexagon six of them maybe a better figure can be here you have a linearity your power supply value you have gain frequency that is the bandwidth your power and your noise and now you control one the other is going to be affected when I start designing an analog block I am worried of a particular RF there is okay this is 0.8 volt mobile cannot get more than that supply oh that means now I have reduced this I do not have enough current oh so how much gain I can get if I did you increase gain by size I mean lower in frequency because capacitance no no I want okay then I must push power that means I must increase currents like I increase current I will increase noise so I have to keep worrying now that how do I optimize most effect okay but you cannot achieve all of it is that clear to you why this limits have been shown that do not tell me that 0 volt infinite gain infinite frequency 100% linear 0 noise 0 power is achieved this is not done okay if you want something from me you must be me okay that is the world that is how world works is hardly okay system is single so in our design that is what the designer job is to optimize the best of it and say okay this is not achieved but this I can do so you cannot have everything but okay if this is your more important parameters okay I will control them but they have the cost of other three or four someone has to optimize this design that is why the engineers are required is that clear why what is the issue I am raising all this I am trying to tell you that automation is always possible in digital many ways because there are fewer parameters to control in analog RF designs there are too many to control and manual intervention is essential because every person will come with some other requirement and oh my god now how do I achieve this so your design approach or your analysis approach should be very good because you have to meet someone specs which will be different from your next that is why the analog circuit essentially is slightly difficult some may say but more interesting because otherwise there is no this is required you know we keep saying digital people that you do not need this you do it automation you give something and it will give you find at the end of the day computer scientists make as good achieve as electrical engineers okay why because there is so much software available you can take download many things and start designing and chip may work as well because someone has already standardized that and can be used here analog there is nothing every minute I need myself to see what is going on okay therefore please remember that why analog RF designs are important or difficult is because of its requirements the major problem which I said you is in wireless application which are the major applications why is a major are sublogue if they mobile use karenge, utna, VLSI or silicon community aapko thank the parents na then they may not like that but as a VLSI engineer say oh thank god use two of them two I have iPod be karo, iPad be karo, A be karo, utna Pasa. So industry is actually working on wireless systems now okay which is more money spinner than anything so we are the other systems like bluetooth, WLAN, set top box you must have seen nowadays almost everyone you have direct TV home VTH this is essentially you have a box there which actually picks up a frequency of your choice and does the set up set top box why it was called top it is put on something set top box that there is intermediate frequency baseband part of radios there is a radio which has come which is called software radio think of it what I said software radio so it is finding different nothing to do with radio per se that is the radio receiver but the word is software radio there are many challenges in mixed signal and why I steam on why did I say last time because that is the technology digital people will force on you whether I like or I do not like is not my choice of analog analog say are a bubble bipolar go but that does not work they say this is the technology nowadays what is the kind of technology we are working on CMOS for digital chips 28 nanometer that is the channel length is of the order of 28 nanometers I started working in 70s when we worked on 50 micron channel length device in my 35 40 years of time now the devices have reached channel length of 28 nanometers 28 in Armstrong's and sooner we may actually reach 11 nanometers in three years first we go for 16 and then maybe we 22 16 and finally 11 if things go all well 0 so that is the technology but analog people will see later longer the channel length is very happy you say thanks my gains are good my bandwidths are good but digital say oh but 28 nanometer that is what Intel has come with all new microprocessors are 20 nanometers so the problem is not the point the problem is bad tools for us good for digital but then you work for those for this that is why it is called mixed signal design is tougher than pure analog why because pure analog I may use bipolar why use boss I have better choice but if I had to work in the money making chips which is wireless as of now for example then I have to go for what digital people will say and that is what we are doing right now if we shrink the device there are many other problems like short channel effects there is a problem of breakdown problems there is a non-linearity problems there is a couple noise problems there is a huge flicker noise I adding now okay so point I am trying to say that there is what is this NQS in device course anytime you heard the word in the devices if I apply something the response time for example if I change by the device does not respond instantaneously you just change the bias external internet takes time there is some issues going on but in system what do you want you want a quasi we want a steady speed so we may not get real steady state we get a steady state which we call quasi steady state but in very low frequency low channel circuits or low channel devices this it is a even quasi static state quasi steady state is not possible non state quasi static now how to model something like this which is non quasi static this is a major issue in modeling in the case of sub sub sub 30 nanometer devices to get quasi quasi we modeled we say okay so what do you do that is the issue at rf frequencies there is it is not possible all over do you solve the continuity equation you say studies now if I do not apply a continuity equation for device how do I get the relationship between currents and the fields a Poisson's equation cannot be because I cannot get now doping exactly so I cannot put in field equation so quasi steady state was assumed in most devices but when I go to a lower channel devices this is modeling so this course has nothing to do with it I just want to tell you why we are worried because they are telling means I am now talking myself analog man and I sit on digital I tell those otherwise so digital people forcing us to think much more now because they are moving in one direction which we do not want but we will have to go kind of this is what I said digital design is getting so much computer added design tools their designs are not very difficult analog circuit still remains a handcrafted art and that is what the world are you say every year it is a art it is called art of electronics it is not art of design art of artist not even science so all cannot become a good analog designer you know all cannot become artists I may actually pen by putting some brush here there but it does not make but normally usually what we understand painting so it is a crafted art how good you are analog designer is individual and that much how much depth internally you create for yourself larger percent of diarrhea it is much easier if larger area is given but they will give very small area too that is an issue probably 100 percent area may 5% analog subcore so that is you know worrying us in every way okay then the design time it takes very high because individual blocks have to be designed time time means what money so many in design engineers will be working so much money here so much money so analog designs normally being smaller even then they take larger design time but they need to meet very stringent steps okay cost of mixed signal chips analog part cost approximately two and a half times that is what let us say in a 0.18 micron as did in 0.35 because it does not shrink as digital everything you know like scale this is 0.5 half care point half care point one nothing happens in analog like that okay so that cost never reduces it actually increases if you go further you know so it is worrying that that analog blocks are costlier than digital blocks as you are shrinking okay because you will require more effort now to design is that okay another problem mixed signal is since you are both digital analog on the same silicon they are connected internally in the substrate so what is good maybe good but what is not it may actually create problem for the other okay particularly digital switches do you understand what is digital 1010 higher the frequency it will do even faster that change will apply to the bias at the substrate that will become signal to analog as a noise okay so this inbuilt noise creation from the digital is constantly through substrate analog and he is worried of you I spoke that is why I say why I say analog particularly in the present era is becoming difficult is okay just newer interesting figures nothing great now on theory this is a very standard broadband network okay you start with a packet for infrastructure gateways show you this is your prime access gateway which is connected to so many applications camera I pad and this is your mobile this is your desktop this is your TV this is your phone this is your laptop so everything is connectable to a broadband figures so that is the lifestyle you all want to be you want to sit in your house work somewhere else and you want to do everything almost by click of your stick it happened this is possible this is possible that is what you all want and this may happen soon and most people are already working on it in many countries like for example in many European countries or in US even in Indiana your pressure cooker or what is called electric cooker you know the person can switch on at a given time and after sometimes switches off washing machine may start after sometime and switches off kind of thing sitting at this again your work in let us take your ladies for work also now it is 50% of the VLSI industries man manned by the other sex very good 50% is a large number 33% they were asking now they are already 50% most silicon this is a cable network what is cable network all of you those who are does not have this be your big TV or DTH home still may have a cable coming from your cable operator which is 4 GHz cable line which is hanging around the road hanging around everywhere finally reaching your home even that can be connected through that you can actually do most of the connections now you look at the video where both analog digital are required the camera cellular video DMA what is DMA network camera IP video DVD D1 DMA IP STD media video surveillance video on demand broadcast everything right now what you see as both analog and digital come this is the fibre links we are looking for bandwidths of the typically around 100 Gbps which is to net 54 OC48 circuits and you may go for multi fibre multi mode and may increase further the transition our ultimate aim that repeater should not go beyond before 100 km is what we are looking for right now every 3.5 km there is a repeater for optical fibre some new fibre lines have to 10 km but most have 3.5 km earlier it used to be 1 km what is the problem if it breaks you will have to remove that link splice it reached validate put another transfer this is that is the issue now we are increasing that to 10 km that is what we are looking for yeah broadband is going to grow fueled by consumer demand broadband access is evolving high speeds because you want an internet very high speed internet that is why broadband is being pushed very highly okay we will move there are three problems in integrated circuits the first problem is power you want to reduce it the second is interconnect how much length I said in Pentium 4 of a first Pentium 1 1 km and the present Pentium or the neon which has come have 3.6 km length so on a smaller chip of 2 cm by 2 cm you get the point it is a perimeter how many times you go like this that is the link the length of the chip is no more than 2 cm so do not think so that is our major worry because if something is going that far my signal will attenuate by the time it reaches to human interest so much capacitance on the line it will just RC time constant so phase margin I got phase margin I got a 1 clock or a signal 2 3 o'clock 2 3 o'clock phasor so there are issues which are called interconnected then of course complexity number of devices transistors are reaching million 42 million transistors in Pentium 4 sorry Pentium 4 first of Pentium 1 now we are going for 800 million transistors Pentium normally 4 which is 142 million the present circuit can go up to 850 million transistors is that clear so that is the complexity we are handling power crisis the major worry in power has come because of the devices becoming smaller there is something what we call leakage problems now in earlier times this word never came to our mind off current off current means when I my for a digital for example when the input is 0 or lower level no current passes in the circuit we say that is what is the stop we say but we assume that time that the on current when it is turned on is much larger compared to off currents 1 milliamp and this may be nano amp but if that 1 milliamp has become now hundreds of or tens of micro amps and this has increased from few nano amps to tens of nano we are closer by even a 50% of the circuit is off and there are 100 million transistors let us say 50 million inverters on that half of them are off 25 million into this off current is not a small power which you thought earlier 0 since the complexity has increased the off current itself has increased and on current has not increased in fact it has decreased because of power requirement so now this is the major issue circuit start failing because of the off current the joke is if you work on 28 nanometers 66% of the power is off power and 33% or 34% is on power that means if you keep your mobile on it will consume 34% of the power if you put it in standby it will actually drain your battery more that is why I do not discourage you constantly talking on mobile because at least net energy of the world is saved because battery is not getting drained is that clear okay as I say number of interconnects are increased enormously there is a noise issue there is another issue has come to trans to interconnect lines interconnect sitting interconnect with the metal layer metal sitting on some insulator they saw interconnect runs but this is met like an RC circuit which means like a transmission line okay now when the two transmission line come closer they have a capacitance in between as shown here these are two metal lines three metal lines at they come closer epsilon a by d smaller a couple so signal passing in one line may actually get coupled to either side this called crosstalk as I said last time so a few string reduce everything closer closer closer this will kill you okay so interconnect issues are very very interesting because they pick up too much noise in all all this work and finally as I said is the number of transistors are increasing number of kinds of circuits we are increasing the board has becoming very big and to maintain their connectivity proper is becoming a very important to design such a large system is very difficult to be designed blocks and try to put on a one common platform which is called system on chip this is the current train system on chip SOC there is also another game been tried by Japan and some other companies is called system inside package sift okay that means you have number of chips put inside one package is called system in package this particular has 28 chips Tony camcorder has this chip which has a DSP memory many things there are four layers seven chips on per layer 28 chips package one single package this is called system in package or system inside where the other one is like is which we call system on chip or SOC where each block is given an area where they are mounted on a single basis or single because system on chip these are possible mechanism which we may work feature it may actually get analog it may get digital it may get men's it may get all kinds of circuits can be separately connected properly so that you may design a large system this is what again we are looking for your time this is 2014 we are going to work on 3.6 g will require for strong control on VTH we are working for 35 nanometer already we are crossed forget that number now 17 gigahertz clock we want to run how much clock we are running and I am microprocessor which is PC 3.4 gigahertz we are looking for 17 gigahertz chips now okay this will be a greatest thing to happen to me this is what the world is looking into 10 meter wide road designing a map of 10 meter wide road for a world at last is what essentially the last two flights I do not know because many of you are not even born in 17 there used to be a famous LA in LA there is a famous serial based on some secret agent called Dick Tracy the name was Columbus and he used to have of course here if you are even at your age you could have seen some of the not not seven bond films he makes lot of tricks on those they were only for film those days all that what was they were showing then like he has a camera he has a music everything on his watch in 1976 serial they showed this okay Dick Tracy in 1998 or 97 Tony came out with a watch which this not only what Dick Tracy was showing in 70s but that much more than what Dick Tracy could do that is the progress it is done similar thing came from Samsung which has a similar watch which has a camera which has a mobile which has of course watch has watch is also there many others you know many times we are invited for tea in the evening by some family and other than tea everything is served so what silicon people this is very important these are actually a silicon wafer with this each is a chip now it is at the horizon okay now if this gentleman is a optimist he will say like a son this is coming out till the full blown has to come but let us not put name someone may be x y of you are pessimist oh it is now shrinking you know it will go down it will now finish it depends on what you are and what you want to think silicon is going to stand till 1950 come what 19 your half the career will be made on that if you join silicon this is what all of us wish Jai Ram Ramesh wants us to do like this by the way Jai Ram Ramesh is distinguished alumina of this institution from the civil engineering department I do not know how civil is connected to environment but maybe public health is one of the part of civil this is called Novadic society nomads move from one place to the other and they do not stick to a place okay so if in a modern era this is possible you can have all kinds of a small laptop or some kind of paper which has every control what you want you can live in a jungle or you can be anywhere your office may be far away in a distant city of 3000 miles or whatever distance you see from good environment around nature everything and you are still working for that company or your home or anything this is what is possible in a very near future finally before we quit on this this is for those who do not want to remain engineers this is my advice executives might make the final decisions all managers do that about what would be produced but engineers would provide most of the ideas for new products managers do not get idea they only manage but engineers get ideas after all engineers where the people who really knew the state of the art and who are therefore best equipped for prophecy changes in this technology so if you really want to remain in best of your minds continue to remain engineers one of my 84 graduate then of course did masters also in computer science not with our department Mahesh Mendei Dr. Mahesh Mendei he is the director of Texas Instrument Bangalore and he is the only Texas Instrument fellow in whole Asia TI allows any academic excellence which has contributed to TI's progress a honor which is academic honor called fellow so he has he is the only Asian fellow TI has a work in Japan Korea China Singapore even in country like Sri Lanka they are smaller this Iran Iraq of course now they are close most of it Turkey of course Turkey may not like to be coalition but Turkey all these countries in Russia so all these countries only fellow is my student Mahesh Mendei why because he chose not to become manager but still start continue to work for the progress of science in TI he has had some 65 patents and three of his patents have got the best awards and therefore he is called director of technology and he he does not report to the MD of the company he starts his own projects and of course approvals are required in the last but he does not have to report to anyone that is his strength so if you really want to remain in engineering discipline you have a good example from ITD you can still reach the best and still remain as active in academics many of the PPT shown to you are taken from Tony Corporation PPT given to me by some of his vice president many of the there is a standard book by professor Ravi on analog circuit there is a EDA company for Cadence so some of the sites have been done actually in India there is not a single VLSI company which does not have IITD students both graduates dual degree as well as postgraduate and since I been here too long most of them by force studied like you have been forced to study with me and they had to study both for me and if they are doing analog VLSI or digital VLSI have must add on my code so I say I control Bangalore and Hyderabad so most companies you see these students come here sometimes give lectures sometimes you so this is latest that is why I get the latest PPT is because of curtsies of people like you who some of you still want to remember me and there are many websites on VLSI available on net there is a book on digital circuit by Raybay which is very good book for digital so that is one of course and finally thank you so let us this is I hope that we will just introduce few things and then stop by now you must have understood why I showed you all this for two days and I wanted to make a distinction for you that you know all other jobs are as good at the end of the day you want to be happy maybe good prosperous happiness in everything you want three car four car everything is fine but the job satisfaction is the first thing you must look for because at the end of the day if you are very unhappy on your job nothing will be as good as you think you may provide everything to your family but you still will not be happy so at the end of the day if you are happy with the banking dueling money here we are writing a free force fair enough nothing absurd or nothing wrong but all need not do that job some should do engineering and be happy if you are learn and if you want to do good and be happy learn what engineering is all about that is why we are actually showing you what is in future what was in past and what is going on so that you can correlate yourself where you can probably if it may be answered as I said we will for next 10 minutes we will quickly go through some of the issues of analog again analog circuits can be implemented into technologies as I said one of course is bipolar the other is mosque as I said earlier also bipolar technologies are not out there are many chips still in bipolar available in market therefore one cannot say one should not learn secondly why I still want to do bipolar because it is called pedagogy that is how we started I learned vacuum tubes and I did not have any transistors you probably do not know what is that maybe look at the big huge 6 to 18 inch kind of glass tubes inside grade plate cathode like a TRT with our tubes 300 volt supply DC that is how we will learn electronics things are changed so bipolar is still not out 741 many of the fans are still on bipolar however major technologies I said is mass so we will concentrate also on mass design because that is what is now going on both certainly have some advantages and some disadvantages and depends on the system requirement one may choose to go on fully bipolar or fully mass because the most systems in marketed are mixed signal they are mostly on mass so we like to see what happens if analog is put on a digital that is why the worries are otherwise I do not see any way let us look you are done last semester a course if not please revise your course because I will not teach devices course in analog okay the basic transistor shown here is an NPN transistor can be a PNP as well the symbol is arrow coming out is NPN arrow going at the emitter is PNP PNP typical NPN transistor is shown here this is emitter which is heavily dope N plus sometime N plus plus then small base width shallow dope or low dope p region which is the base connected and a little lesser dope than N plus is the collector region and this is the symbol of currents we are shown IB enters I enter so is IC enter this is the symbol in real life these symbols are no meaning why because current can start or the base their circuit wise the current can be shown only starting from positive terminal of the battery and should end at the negative terminal that is what the circuit is word about so irrespective what happens inside or whatever you may say for the device actually currents will start from power supply and we will go to the ground that is the way it will happen now you may have to say no but you are showing this symbol and the actual current is this yeah that may be electron current going down but the actual current is going up is that clear so symbol in devices and symbol in circuit may sometimes vary because of the carrier which you are going to use in different devices this is a symbolization but do not worry this is for device in real life please remember circuit always will start current from positive terminal of the battery and will end at the negative to form a circuit unless it returns no circuit and unless it is formed no analysis no current okay so there is a universal thinking in bipolar as you must have learned that the emitter current is always some of base current and the collector essentially what we say when the emitter electrons emitter injects electrons part of the electrons are recombining in base okay constituting the base current and the rest will go to the collector however in this there are some leakage current we are not added but that may happen because there are two diode they may cancel so basic idea in case of circuit please take it these are circuit we may in reality devices small changes may occur but in circuits emitter current is always some of base current plus collector this is our universal theory we also know the collector current as I just now said not all electrons starting from emitter each collector there is a transport essentially because of recombination because of the efficiency of this emitter junction and the base transport it does there is a term which is called alpha T is base transport factor and emitter cannot have 100% efficiency so it has if emitter efficiency gamma and the product is called alpha and IC is equal to alpha times I please take it these are circuit equations some modifications will be done in real life in case we need leakage currents to be added but normally these will be followed in most we also know that the collector current divided by base emitter current is alpha but collector current from this equation now use I is equal to IB plus IC in this equation and then you will get IC by IB is equal to beta which essentially from this term will come alpha upon 1-alpha and beta is essentially called common emitter forward current gain is the major parameter in all our analog circuits beta how much is the why because typically the inputs will be given at the base and how much beta times it will provide you the collector so larger the beta larger will be the gain and therefore it is called gain typically gains can be as low as 234 or 5 and can go up to 500 to 600 this is possible why 500 600 you cannot become alpha is equal to 1 beta is infinite but alpha can never become one because alpha t cannot there is there will be time there is a finite time or a combination time in the base and there is not all electrons there will be reverse current also coming from base to the emitter so all gamma can never become one since gamma can never become one alpha t can never become one alpha can never become one so beta cannot be infinite guarantee alpha will never become one so as high alpha you can get 0.999 that may give you 1000 is that correct so maximum possible alpha you can get in most technology of device may be of that order this means not more than 600 500 beta is that correct this is technology limits if you can do better some day yes you can improve but that is very difficult I am not saying possible we also say if you want little more accuracy IC is not only alpha ie plus some collector leakage current which is called when the emitter is open sorry collector is open whatever is the collector sorry base emitter junction is open whatever is the collector current you get is called ICO okay devices if you have no if you do some of you do not know or not understood you come me separately out I will explain the devices much more detail if you wish so I right now assume that in this is what I can use most circuit but if I want little more thinking I may add a term ICU ICU of course is decided by ICS which is reverse saturation current of collector junction into 1-alpha r into alpha r what is alpha r alpha f is that is collector acting like emitter and emitter acting like a collector is called reverse operation so alpha is the reverse operated alpha of that so IC by ie opposite way if you do it it is called alpha that is emitter becoming collector and collector becoming essentially what saying in normal operation base emitter junction is forward bias base collector junction is reverse bias if you do the contrary base emitter junction reverse bias and base collector in forward bias the carriers will come from the other side okay and that is called alpha r so it can be proved by device theory that ICO is reverse saturation current ICS into 1-alpha r alpha r and that you can evaluate ICS by measurement you can do easily just open that circuit and measure the current in the actual circuit that the ICS you also have one Kishav law always followed BCE is if you see this BCE and this is your BDE and this is your BBC you can see from here at between the two nodes you can only one voltage between any two nodes you can have only one voltage between this collector junction and emitter junction if you have a voltage BCE but if you go through the other side of the loop you go from emitter to base and base to collector then the sum total of base emitter voltage plus base collector voltage must be equal to VC and actually this is the fund that the operation of the device which becomes saturated that both junctions become forward bias and therefore VC goes down is very interesting maybe some day we will explain that okay that is what this digital circuit will want okay that VC should go down to 0.1 volt because that is the zero state of the logic okay in analog we will never like to do that because what did you yesterday I showed you figure I want to be in linear region of V0 Vain characteristics all the time okay therefore I will never like to do to saturation area I will remain in the linear area all the time is possible so this equation is again valid all the time VC is always equal to PBE plus BBC okay this is Krishach law between two nodes same voltage can occur okay the second third issue which is of relevance in bipolar there is something what we call large signal model but what we are interested later is small signal model but let us see what is large signal we said this is what we are showing you right now DC value essentially is called large signal model typically a bipolar transistor can be shown as base emitter junction is a diode base emitter junction is a diode and base collector junction actually has a collector current which is beta times IV so it is a current source depending on the base current which is decided by the diode at the base emitter junction is that correct whatever VBE I apply e to the power Q VB by KT is the diode current flowing in KT if it is different device and different region but the diode current is the base current is that clear is that clear diode current is the base current and beta time that base current is collector current that is our okay I must show you IC here IC is beta time that is what equations we wrote that is the representation of what I wrote I am showing you in this circuit now why do I want to always show some numbers as representation because at the end of this when I solve a analog circuit it is a circuit there is no device there I cannot use diode there is that correct but then I have to write exponential term this I cannot solve in a circuit such what should I want I want equivalent of that in a circuit so I say okay when the diode is on it is like a battery of VB on which may be more than 0.6 volt cutoff is 0.6 may be 0.7 volt which will assume so VB on in all circuits when it is this will be assume 0.7 volts okay if it is less than 0.7 we say it is a going towards of state now if it is less more than 0.7 it will go to saturation say 0.75 device may actually saturate so this 0.7 volt is not exact number actually whatever bias you are accordingly it will calculate but for circuit people 0.705 or 0.699 is no meaning they say 0.7 is good enough is that clear so something which I am now representing is for circuit analysis device people may not say correct for us that is good enough similarly if you are looking for P and P since it is opposite polarity device the diode is shown opposite where P lower and above here P above and lower is that clear so it is just NPN P and P it represents it the base current if you are really looking for is the saturation current divided by beta into exponential VB by VT what is VT I wrote VT is KT by Q okay is called thermal voltage VT is called but this I will stop writing afterwards because in VT in the mass transistor is what the threshold voltage or turn on voltage I should not confuse that VT with this VT just now I wrote VT but later on I may use KT by Q everywhere so that node is giving about threshold voltage of mass transistor and VT here as thermal voltage so similarly I can say VB on IB beta times IB this is for P and P is that okay simple model what is missing here there are many important parameters right now I am not ready for example there are resistances, capacitances whatever is going to happen right now I am not sure this is called simplistic model of a BJP we will add on terms in real life oh so it might occur add something now we will what is the way method we will first many times what did we do we actually looked at the device and found some numbers and added there what is the inverse way we did measurement and this simple theory did not meet you have got a card and he had for a resistant I will drop the exam so there are two ways of learning any circuit one is do it and do not find the correct theory so add theory from your side which with the model or you create a good model and then verify on the way to work okay it will okay so when we give a lab many students ask me if there are up now with theory to put on your lab they do nothing happens because you do first and then when you start looking at theory oh now I understand why it why it happened or you can even start thinking earlier so do not go and tell the lab professor has not taught this how can you give me excellent you do an excellent otherwise okay and then learn the theory back or learn the theory first and do excellent later so it depends on individual choices but this is where I look at it so every time we used to give a lab people used to say apnita be Khudinani paraya. So this model which I showed you is called large signal model one minute and this is called small will come back later next time this is most important thing which I want to use this is not for BJT for every model but here it is shown for this we will say the total base current let us say is represented by capital I small b is that correct total base current is small signal current which I represent at small I be okay plus the DC base current which is capital I capital B so small signal plus DC is equal to the total current is that correct so total current is represented by capital I small b equal to small IB plus capital IB is that clear this is my symbols say if I write one way or the other you must understand what which terms I am writing in the case of collector there is some issue because see you know Chota or but I very difficult to draw okay so I made smaller one as a bar to show that so this is total IC current which is equal to DC Cal collector current plus AC or small signal current IC this is a transfer output characteristics of a transistor will come back to it the next time but most interesting part from the circuit why I showed you this just now before we go ahead I plotted collector current versus VCB that is output what is VCB in that figure if you see my VCB which is the in the common emitter circuit this is your output voltage DCB is that correct this is your input current okay this is your output current let us look at it this is your IC this is your VCB if this I ground this is my output VCB that is what I said okay oh there I am I may made a mistake I should have I am sorry VCB I am sorry I apologize okay so if I plot out I kept saying it but I think in writing I may mistake so if I plot VC versus IC current which is the output characteristics of a common emitter transistor then for different base current IC different characteristics as I increase base current the collector current beta times IB and in non cases it may not be linearly related it shows different regions of bipolar operations however the issue which I am going to show in real life if all these characteristics are different IB are extrapolated back okay they all meet at a single voltage which is called early voltage what is early voltage in device if I start increasing VCE essentially I am increasing VCB please tell that VC is equal to VCB plus VB I may fix but as I increase VCB I increase VC is that correct if I increase VCB as I increase what will happen to base collector junction it is depletion layer will start enhancing depends on the doping on both base and collector my majority it may deplete first towards collector because it was kept N- okay so most of the voltage will be sustained in the collector region but emit base will also start getting depleted is that correct and some voltage base may get punched emitter and collector may get shorted to a depletion layer that is called punch through or called early voltage is that correct at that voltage at that VCB or VCB we called the device is punched okay this is very important parameter for us because if you see this slope please look at it this slope for any current this voltage this is very high typically we early voltage will be 50 volt and 100 volt VC will be 5 volt or less power supply is at best 5 volt typically 3 volt 2.1 volt 1.5 volt so this 50 volt divided by the current is what voltage divided by current is what this slope resistance which is this characteristics I am drawing output so what resistance I am talking output resistance so if I am given early voltage I know the output resistance of their transistor immediately is that correct since I know this at any given current this divided by this is my resistance and they should all show roughly same slopes I mean same because they meet at same point to R0 varies with every base current to some extent because your slopes are different okay but majority at that current wherever you are operating you will know what is the output resistance of the circuit so from the circuit point of view if I am given a early voltage indirectly I am telling you whenever you will bias it at a given collector current I know what is the output resistance I have chosen is that clear that is why I showed you this slide that many a times R0 is not specified but early voltage is specified okay and from there R0 is known to us is that clear that is how we will actually start working later thank you for the day