 The course objective of course is that course deals with basic theory of analog already second year analog circuit course must have been done so nothing great will happen from there basic things cannot change however from there how do you design a chip that is the course is trying to but unfortunately the word design itself says that it has to be it is not available that is why you have to design that means you do not know the specification a priori so when you are given a spec how to meet those specs will require lot of understanding of devices as well as circuits because then only you can actually meet those difficult specs and therefore design requires some understanding of basics of both devices as well as circuit devices to a smaller extent but circuit to a greater extent so this course will try to give some idea of good design principles and to simplify the design process itself this is course content available in the site itself however there is some you know a to d and d to a some parts were reason because that was old course design in which there was mixed signal circuit was part of this course but now a new course is running mixed signal itself so we are removed that part so we are little more time to do earlier things better okay. So basically we will talk about mass models why analog models are different from digital models or how bad or how good they are we look into spice model so all of you should be aware of spice I will not teach my so we will talk about gain stages both with NMOS and CMOS we will talk about cascade and the word cost code as the word goes there will show you we will talk about basically references voltage and current we will talk about differential amplifier which is our bread and butter and we will talk based on that opium design we look into frequencies in size VCO based or PLLs look into little bit this year on interconnects because this is becoming a very tough situation in 2010 or 11 I had will look into some testing layout issues and also show you the current context this word low power or actually the low voltage low power is written specifically because the misconception among designers is that low power circuits are interest more interesting it is not actually it is the low energy the worry is on energy not so much on power okay power into time is energy so energy is what is worrying us the battery stored certain amount of energy it does not store power okay so how fast that will consume we look into it then what is this low power business the books which I use are not the only books which you should see hopefully yes but I like this Razavi's book by basic analog integrates the kids most of my basic part will be actually taken from Razavi's book okay which is a very standard all over the world I have a addition one but I think now there may be addition six four five order it is by the latest one then there is this book is as I say mostly on the analysis part very strongly then we will talk about something which is more practical which is a book written by Baker Lee Boyes is one of the pioneer researchers in the area of analog we will also look into a very old book old in the sense it was available in my time so old that of course addition has changed the authors professor Gray is still still Paul Gray is still there but the other mayor her days this keeps on changing my of course is older one but the I think this new ones which Hurst and Davis are joined this is one of the oldest book on analog integrated circuits and Paul Gray was the chairman of a department Berkeley UC Berkeley also then the president of Berkeley is still there because it's old 81 years so his book is one of the best analytical book as far as the feedback here it goes those who are interested to know more about feedback please carefully look into this the only problem is they are more from the old era so they are much more bipolar circuits though they added now most in last 10 years but still their emphasis looks to be more on bipolar so I think that's the only reason why it's not so very popular my course itself so I cannot say bipolar so when there is a book by smile as well it's not available in the market the reason is that it's old book in India hardly anyone knows about it I being the one know about it when I was in abroad so I purchased one and many of the interesting research in the area of analog particularly low power or conveyor systems I think came from a smile and wise people he's still with why university so you can go on his side and figure it out of course some journals and some conference papers there are other books are appearing in the market please if you have you know some book which is good maybe you bring to my notice I will also look at it but course doesn't require because what I cannot change amplifier whether they are two books whatever they say amplifier will remain the way it is so don't worry if you are one of them is okay okay so basic analog design with CMOS and analog system will also see something about low power low voltage what is layout issue conclusion this is only some overview so wireless is the major driver for us all VLSI designers are actually indebted to people like you who use mobile may be two mobile these days iPad iPod whatever you talk why and all the Wi-Max Wi-Fi whatever other hardware you create this is the way money is available and that's why most of the chips or most of the companies except Intel for no good reason they fixed themselves to microprocessors and I think another 30 or 50 or they may not leave that okay but all other companies have some way or the other has shifted to wireless products call com is number one dot com is number two and lines of them even TI which was more signal processing have finally entered wireless world last time yes so everyone is looking into wireless so that is the major requirement and there are systems which are specific optical system people are now looking into changes from electrical signal optical it is not news quite some time but more results are now coming so there are many systems which are optical systems which may require our effort at least to interface them there is a effort going on on semiconductor 100% optical signal system so there is no conversions no losses but the material they are using is mostly 3 5 materials but I am partly silicon but everything on so a link has been created which is 100% semiconductor based optical system and no transition transactions the other area right now is sensors and if you connected to wireless and that new word wireless sensor networks as if it is great sensors were known networks were known wireless was known you combine you are in the world top 10 that is what this so you are right now people are working but sensors can be of any kind any try any energy to any energy the sensing you have to sense there is also a cat with the what is the word transducer and what is the word sensors there are lot of fight goes on basically sensor should only sense that is the word is but most people believe sensors means a transistor with a conditioning circuitry or what you call amplifier signal everything on chip or everything together is a sensor this is the way they think I am not saying correct so there are many systems which are requiring sensors now based connection to circuits so these are markets then of course it helps high speed microprocessor 4 gigahertz if you give you say you need 6 you need 6 you say 10 why because that video game I want to kill that person faster somehow so that microprocessor speed somehow is the marker for everyone how fast so huge effort is on high speeds and of course to come match them then you need data transfers as fast as this is asking you need look for high speed memories so what is the difference between digital design and analog design in digital design if you are I think you are done some digital circuit but the other course is running 6 7 1 where it is a design so there we keep saying that look digital design is basically hierarchy that means I can have system break into smaller once I design grid to smallest part I design back bottom up so and gate can convert to XR XR can convert to large and we can go to any system okay so the idea in the digital system once designed you can really you do not have to redesign because anger does not change very much except for his driving at his current how much it means or dies up so these are more you know what you say cost semi-custom available you can use it analog there is no such things every system you ask you have to design it so it is called custom design something every customer requirement has to be met therefore analog designs in general are custom design and in general people are now trying to make equivalent effort like can we make VHDL instead of this HDL analog hard high speed hardware description language can we do similar silicon compiler for analog so there is an effort going on to do replication of digital into analog but as of now most of the circuits are actually designed transistor wise component wise that is the strength as well as the strength in the sense for a teacher that is the best thing because now he sees transistor in digital you do not see transistor a cold Ligia Hogyak a barator Hogyak and Hogyak XR either though transistor became so something you can see what is happening is analog and therefore you can design oh if I change size if I change mobility I change VT what will happen is my GM is higher so I am looking one to one what specs I am looking for that digital does not require because of course is the easiest designs okay so the point is that it is a custom design and therefore very interesting because every design is required some way your so-called man satisfies him his ego if you say yeah I understood another issue but he feels very comfortable that yeah I am not that is why all this quasi pulsars the recent experiments what is great going on if that divided at on is not existing you mean world would not have been the world is still there now we are worried is that kind of Higgs Boson is available that makes fun for us because then it says oh statistics is something like this it follows but it has it is like that but it has a mass so it is not like a fermion so this satisfaction that we understood is always with us and I wish IITNs do not leave this part in their careers or in IIT remain do not become Robots remain humans if you do not know few things is okay but what you know you should know better what you do is irrelevant but how do you do is okay what subjects you do life what you do is very irrelevant otherwise all kinds of people would not have been there successful but how do you do matters so work for the best of yours in whatever you do that is that is human and if falter more to learn in analog circuit power and speed like in digital is also important the word in the speed in analog is converted to word bandwidth which is essentially digital in small speeds few queries questions are always asked why analog so in 1980 many of the digital system designers they started saying analog is dead that is it end of it but 2000 you see more and more papers more and more industries are entering analog okay so something has changed or something necessitated that analog design we looked into the reason probably is we are now trying to see harness more of natural resources of natural systems we are trying to play with them and nature essentially has is everything in analog that is why the question came whether big bang theory is okay or solid steady state theory is okay because nature does not like bumps it always goes one after the other that is how we became human from all the other races so nature is analog so even if you process every signal digitally at the end which is better in many cases the front end will be always analog because signals will be analog so analog is a necessity because any DSP ahead will require digital data which it can receive converted from analog so that is one reason here is an example I have an ADC and I have some input analog if I convert it through ADC maybe I will get the same to table for it or the data something like this which may be fed to DSP the problem is that the signal here the strength of a signal or amplitude when you convert through ADC and if you are done ADC sometime you know the there is something called INL DNL so it how much error it will create because if it does not cross a threshold it will not go to the next stage next state so it may remain in 0 it may not show you one where it was so it should cross so it is very unlikely that every time you will get a correct conversions okay because analog natural signal may not be known to you and has it actually known amplitudes so the best way is therefore amplify analog signal amplify once you have amplified the signal you are almost sure what are the levels and if you now convert it and maybe other components some frequency components you can cut off from there other than the desired signal you put a filter path through ADC and you get a digital data you are guaranteeing efficient way of converting an analog to digital that is why you need an amplifier need a filter before any DSP or ADC can be applied so that is why analog cannot be just brushed aside there are natural signals required digitization will require at least amplifier filter and in ADC now further going ahead there are sensors of all kinds mechanical memes which is very popular these days in our group optical thermal and they all energies are transduced into electrical signals because we are electrical we can anyone can convert mechanical to optical and get away but we will not probably there because we will like to see something signal micro volt nano volt or some volts or some currents however most of the outputs of sensors when converted or otherwise without amplifiers will be very very weak and therefore has huge percentage of noise on that so obviously the noise part has to be removed so the all the analog system which we create must be low noise because otherwise they will pick up noise and add noise to it therefore the analog signal people must worry much more on the noise than what digital people bought it is also not correct but this is what I say this is my statement digital data normally gets if you transmit very long unless you are a repeaters it gets a torture or call distractions so it is better if you have a trans receivers of analog kind because they will be faithful to your signals always how much additional hardware you will require and how much money you may have to pay may be another issue but analog transmissions will be take a cable home television you have a very good signal coming you see a beautiful videos you actually connect a normal computer and put a TV in this you see it gives a good figure but it has a huge lines in digital because the pixel to pixel it picks up now this is essentially one says that analog signal processing is far better than digital signal if you see a hardware hard drive disk many times over the time because the magnetic in many cases the signal becomes very weak data is very weak so it becomes very difficult to know once and zeroes there and therefore what you read may not what you wrote so you need some amplification prior even for you read wireless for example the antenna which your mobile has a very small antenna which has very little directives that means it has very small antenna games so the signal you receive is very weak so the first thing you have to do is amplify because otherwise that signal is less than few micro volts so your circuit cannot actually behave so you need an amplifier right there after and so I am trying to convince you that why analog micro process and memories with ultra high speeds use clocks and signals gigahertz you are saying 4 gigahertz as system clocks are for Intel new processors may be 6 gigahertz now these kind of signals at such a high frequencies do not remain pulses they actually get mashed up and they look more like analog what is the difference word analog means continuously time varying signals are called analog step signals are called digital 0 1 or may be multivalent whereas in analog amplitude keeps varying or frequency keeps varying with time that is a continuous so your clock if you see now it is more like a continuous kind of this there is no fixed wave it is something like this baby as much you may like you are still doing analog signal processing even in the high frequency the interconnects which is the major worry right now on any single chip right now they are huge RC or RLC parasitics now transmission line effects are very very strong and if you are done your theory of aim with which I wish you have you will realize that transmission line theory it creates you know the impedance match the reflections VW are words which we use in there they do now come into picture in our own circuits now and these are basically analog signal so what we are saying even in the high frequency digital domain you are doing analog signal processing any way if you have a memory I hope you have done some course in particular SRAM or DRAM you say there is a or any memory for them there is a sense of the idea of sense amplifier is you do not have to see full voltage swing before output is given to you so a sense is one or zero faster so when you sense it it has a some kind of a defam going there which is an analog device okay so you look at systematically any digital hardware even now you will find one way or the other you are directly or indirectly using analog processing so learning analog is not very bad worthwhile at least call come Broadcom look off to our children for example you have a cable and you are inputting a signal V in and expecting an output V out it is a good V in signal good pulse is going but what you see at the output if the cable is lossy which it will be most cases there is nothing called lossless cable low loss cables is possible but there is nothing called lossless cable so if even if you are lossy the output you are going to get is not digital you can see what signal you are actually transmitting so essentially anything now you do at high frequency in particular you are actually worried more of analog problems than digital okay you must know in mind that is this course really relevant other than the job which of course is I mean so the question finally can come why analog question for me is analog design more difficult than digital if you are asking me when I teach analog course answer is yes the reason is obvious in a digital design if you mostly it is inverter based or not gate based if you see the voltage levels which are allowed in digital so let us say VDD and 0 are the uppermost and lower most signal up to VT 0 can go and even up to half of VDD upper voltage can go still it will be recognized and 1 and 0 is that correct so there is a huge noise margin available so signal is not reaching peaks are going not going to 0 does not matter 1 0 does still recognize it because there are four corners high speed Cmo in case of CMOS may be slow high slow slow high fast and other four as law that margin is too big if you fit inside that four corner you are safe everything will work essentially related to sizing as well as temperature so if you do that process and this together if you fit within that enough margin is available to you ideal is which has VDD by 2 margin anything less than 1 and anything greater is 0 so it is a fantastic system so you are not worried too much of course there is a tradeoff still goes on there their major worries power connected with speed larger the power larger will be I mean it will be high speed this is very obvious to you here in some case because in most circuits the current which you are using is to charge the capacitor larger and the current CDV by details larger time will be smaller as great as that so faster means push current higher current higher current means higher power so it is very simple that power cannot be low as well as speed can be higher but that is what digital people want and that is what we keep doing that how to beat the system low power high speed how do you do that is the game so how to fool a circuit to do that externally you feel that I have achieved it internally things cannot be changed but externally you still feel oh I have achieved low power and relatively high speed the games of course you can have third parameter their area of the chip or area of the power circuit which can barter with that and can adjust to one of them whereas in analog it is not just bandwidth power it is power frequency gain precision which you call rates supply voltage all of them actually affect the outputs so now when I am designing something if I catch one the other may go a wire if I catch two or three the other three may not be within my hand okay and therefore design of analog system really requires thinking that is why I said that word thinking more essentially means yeah some people like thinking so for them analog design is simpler because that is what they want but in general people want to bypass thinking then digital are the best analog are not there are more problems with analog as well analog circuits are extremely sensitive to noise and crosstalks crosstalk I suppose you little bit of a bear if two lines are going together the signal on one line can interact with signal on the other okay that is called crosstalk the worst crosstalk occur if the signals are moving opposite direction if they are in same direction lesser crosstalk if they are in opposite direction it is x minus minus y so x plus y kind of situation so crosstalk is major worry in most of the circuits now digital or other digital is worse right now you are putting too much of interconnect there too many lines going on particularly like DSP it has a more lesser circuit mode interconnects so now at such circuits you will find the problems are only on the crosstalks so how to get rid of them one method of course this is just that put a ground line every between two signal area the paid price which we do even now the noise any line picks up you know like you put a wire it picks up some voltage essentially is noise voltage thermal it is nothing else analog that noise is there is no margin there so any noise is also a signal so if that goes it also gets amplified or whatever modification noise also will get modified nothing can be done in digital device second order effects but now they are also important in lower technologies but earlier we used to say that they will not so much important because of huge noise margins available in the case of digital analog any variation threshold go is goes by less than 0.1 volt current will be proportionately increased by that much square now this means now suddenly you figured out small change there we did not carry here that has immediately GM has changed bandwidth change sometime it will not within what you want so the next stage may not work so there are issues which only analog has to tackle so automation becomes therefore difficult I am not saying it is impossible difficult because every case has to be 100 even in layouts which are generally done by layout editors final before mask is made most digital people just go through a layout editors and generate patterns very fast analog even if you do once you will have to make 100 time intervention oh this may not work better okay try this now okay resimulate again with the new one exactly so there is game in analog layouts also huge problems in analog layouts we shall show you this part later and the models which are good for digital are no good for analog we show you some of them for example there is a saturation parameter called lambda which will be in the current device in the open design case it the change in lambda is lambda to the power 4 in the this change so what you thought 5000 gain you may get 5 or you may get 500 for it and depends on which way lambda moves lambda change the R0s and if you make products it will go to the lambda to the power 4 digital nothing called such lamb we actually leave lambda here that lambda cannot be left so analog designer therefore in my opinion is a very smart guy who uses his experience and to a great extent intuition this is what humans are we have intuition that is how we differ from animals if we are no intuitions will be as bad so when you use even the simulators you have to have great experience back knowledge and intuitions to design the newer system that is the difference between analog and digital now what is major worry for analog designers is this analog independent analog chips are very few demand opens are made and made and they are sold only instrumentation people buy them very few such other systems buy opens per independent so I cannot have best of opend design like 8576 very low noise opend I can design I can make I can sell that also as they are on a board on a single chip on that but it total mixed signal system 80% of the part on that chip is digital or maybe more at times so what who will decide the technology the digital the digital technology which we call smaller channel length technologies nanometers 11 you want to go 0 nanometer mass transistors now so you want to reduce but surprisingly when we do analog design we figure out the largest the link better for us now here is the first conflict comes I want to work on 0.35 microns they say work on 16 nanometers here is an issue so the technology will be 16 nanometers and now I am told design your analog as good as what I am asking on this technology which is not good for you so that is the biggest challenge analog if you are left alone maybe I will use bipolar which are the best analog components but I will not be to ask to do that I say okay see was of course is the best big for digital circuit and then whatever we do analog has to be used now has to be designed only on CMOS it is not that I cannot design on any other technology or better or worse by CMOS even better but because 99% digital circuit are digital based I will have to work on all the time on CMOS because they work on so there are issues which certainly are cropping up not because analog is weak or something you are given a bad tool and ask to design a very good system that is where but that is the interesting part because it is not easy it is not easily thinkable so you are best comes out okay I can beat the system at least I reach what he was asking so finally in the end analog IC design is successful implemented analog circuits and system using ICs that their unique features are geometry is an important part of the design this is most important which is nothing in digital but in analog the geometry the layout is the most crucial part of the design even sizing is very very crucial you create electrical design from there you go to physical design and from there finally when the chip is made you test the you have to create test vectors you have to test so all the three part as in digital is also how to do the case of analog as I said they have to be implemented mostly for mixed signals and as I said 20% analog 80% digital and a chip so 80% majority majority governs democracy because of that analog circuits have to be analog design has to be on a transistor or a circuit level more importance has to be given there is a pass means after I design and I fab and I test okay then I see what specs I wanted and what did I get it is called one pass most digital circuit because of the experience and expertise available now across the world one pass most circuit will come out at best to inverse designers if you are not a good designer that means we are not good digital designer that is what you should avoid in my class but that is what the industry is good who can copy best is the best digital design you see or the design marks are nothing better okay it has work for you also whereas in the case of analog it may require two passes it may require even three passes so cost is very high for that so that is why I keep saying analog so what are the systems in mixed signal or analog we have in analog system which we have amplifiers filters barretters oscillators or frequency synthesizer the new name multipliers PLLs phase lock loops voltage current references sample and hold circuits A to D and D to A converters high speed IO interface this is another area where much of the work going on is high speed IO and DC to DC converter now this word is very interesting it has been asked by me across IIT faculty interviews for assistant to regards to them who did not answer if I have five volts old supply and I want two volt or one volt put a pot we are done in secondary lab it register like a divide curve the old military so DC to DC can cut the DC say AC joy is a big cargo or the mhambi can consume or be they are not wrong this is one important parameter so DC to DC converter and it is become very important even for digital now because on a digital hardware now there is a what we call power supply unit or power management which essentially create where are variety of voltages for variety of blocks of the digital part so there that is analog part that is why I keep saying analog is secondary like that but we want to have analog design automation some of you can think over it we can have automated layouts we can have better simulation techniques then synopsis or cadence giving you analog you want to create hardware description language similar to digital if possible and the best of course is you design and keep record of that is called intellectual property probably you can use it you can sell IPs itself do not make chips design a IP test test and say okay this is doable so a opamp from at mal you can actually buy an IP for an opamp you do not have to design you find out from space which at mal number matches required you just ask pay hell of money for getting that but the effort of design is 0 pay for it someone else does not really use it there is another way of doing analog designs most Indian and abroad companies actually work on IPs either they create IPs or use IPs those who create IPs IITN should join them because there is worth of effort is interesting if you look at the signal and information processing application for analog almost every telecommunication multimedia automotive electronics biomedical electronics consumer electronics neural networks sensors sensor networks space and military applications or electronics and of course in all digital and digital signal processing itself now you will require analog study there are two kinds of mixed signal which probably many of you are not aware most of the teachers here are including me make signal means mostly digital part analog but there are other kinds of circuits available which are useful also particularly for newer applications of bio which are neural based there most of the core is analog and some inputs or outputs are digital okay so these are also mixed signals here analog is a major component so neural processors if one example we show you the figure and we will also show you some comparison of analog digital this is a typical neural processor okay you can see from here this is your computer also data from where you can create digital data you can have a DSP some kind of neural DSP processing convert to analog then most of the processing is a neural analog then again convert to A to D for feedback to digital so that the system is stable as well as to spike so if you see it a digital part as vector quantizer some code book generators which comes from PCs and through neural processors then there are a host of interfacing required timing control digital requires so is analog requires if you see the analog part particularly it is a neural processor requires some kind of vector quantizer again and it concept of synapses and matrix if you have done a course on neural networks you know about it maybe I will show you as well you may require summing of currents for neurons you may require sample loads and you requires encoders and WTA cells communication people know much about the word WTA what is it there is a famous song from 25 years ago Abbas song first song winner takes it all WTA of course in bio it has another word but in case of this winner takes it all WTA so it is a majority circuit which takes winner these are the part of a neural processor which requires more analog processing than digital this is the old slide of 98 so it is not very valid the point we were trying to make then why it is 98 can you guess this word 98 in 1998 this course was written by me and first time taught in IIT or other any IIT everyone copied and kept saying we have started fair enough all teachers do the thing you also took someone from Sanford or MIT and then we say we have done it other IIT is doing for me saying is equally good at least they have seen my course is good enough so this was the time when so this was a old slide so I just wanted to show you so from this you do not have to go the idea is to show here is that everyone believes that the analog processing is costlier it is not true if you look at the million connections updates per second or instruction calculation per second analog is better than digital okay so to some extent this idea should get out that digital systems are far superior to analog system this is only my word for you because people have started believing that that is why digital is popular no it is really simple cheaper that is true but otherwise if you are larger processing even this can match you as much but with larger analog there is more problems so it is not catching up but by the theory goes analog signal processing will be far better any day you see the same numbers human brains require 210 to the power 9 million connection updates per second we are still analog at least we are reaching 20,000 digital 45 so we are no way reaching to the nature analog at least we are coming closer to the some extent analog is still very much relevant for Funda people this is taken from a smile face this is just to give you I want to make a similar logic design kind of thing for open this is my aim no one has done it no one has succeeded you have a mixed signal concept this is called top down design bottom of implementation as we do in digital you want to see can be doing analog this is the flow from concept you can create architecture each architecture can be created to circuit blocks you should have some evaluation blocks feedback each and from there to circuit maybe reevaluate and feedback the flow which we follow in digital can be follow similar way analog is ultimate for us we are not right now we do have a design so if you look at the analog here is this typical digital inverter on your left p-channel device and channel CMOS inverter depending on the input low or high p or n will be on or off correspondingly output be one or zero very trivial inverter circuit which is digital the V out may not be as VDD V out high may not be VDD V out low may not be 0 but possibly we want to make it and CMOS it comes very close to 1 and 0 as they are whereas if you look at analog the basic circuit is an amplifier actually this is also an amplifier there is no difference I will show you the what is the difference this is an amplifier which has a resistor which can be a transistor and you have a n-channel driver please remember the word driver is used by us which actually puts the input this is input and puts the output so it drives in this case when cannot say n-channel is the driver because other signal signal is also connected P whereas in this case this transistor is a driver in NMOS inverter yes there will be a driver transistor in a load as it is this is like an NMOS inverter so the what is the fun part in this is if I plot for an inverter or an amplifier V out versus V in you have done this many courses this is normally VDD this is normally VDD there are of course as I say five regions but the three shown here anything V in less than somewhere here V out remains high anything beyond maybe sorry VDD is here not here somewhere anything beyond certain value of V in the V in becomes VDD this becomes 0 this is what normally inverter shows and we normally do not worry about this part the reason is we are only worried about these levels 1 or 0 so input goes 1 output should go 0 output input goes 0 output should go high it transits we do not care too much we do but not so much if you see the gain here DV 0 by DV in is how much 0 same way here so this is 0 in these two regions but what is here DV 0 by DV in which is gain which is negative value is my game so if you are looking for an amplifier obviously you cannot operate on this region and this region you can only operate in very small and if you use a CMOS you can see this will be even sharper like this this is very interesting that means DV 0 by doing very high in transitions so analog circuit only work in this small input range that is why small signals where digital can go from 0 to VDD so gain part only comes in a very small inputs so we are worried all the time about this region in the case of analog is that clear to you so the transistor must be remain biased in this region to keep amplification in digital you do not bias because you are not interested in games anyway of course it does have influence on speed margins I am not trying to say digital does not get affected by that in fact depends on size it may shift and it may reduce the margins but typically digital we damn care because we are only interested in the two ends analog we are only interested in between okay which is the game function so one has to accept that the first difference between the two circuit is the input range otherwise this can be used as an inverter okay this this hole as can be used an inverter so as you can say this is an inverter because it allows you to shift VDD to ground whereas this will input is limited and the bias which is not shown here is exactly in that range in which gain is possible is that clear exactly that is the reason why analog is interesting if you see comparisons the digital circuits are highly nonlinear you are just seen the characters very nonlinear linear means dv0 by dvn except at the edges it is constant okay so linear okay another second year student who have passed why is equal to mx plus 3c is linear but it is not a linear system do not confuse between linear linearity and systems okay so it is a highly nonlinear high noise immunity immune to power supply variation because I say margin a high VDD upper 5% who cares and one bit at a time is the information transfers no worries if you look at the analog it is very linear that is the game gain is required extremely sensitive to noise now you can see anything now on this will also get amplified so any small signal also has a larger game seen by it so now part from signal any noise also will come to you okay whereas in the case of digital damn care okay so it is very sensitive to noise and therefore worry any power supply variation is also worrying because it will directly reduce the currents and therefore GN and carries more than one bit of information okay and therefore it is multi bit transfer there are issues right now which I have worked many years ago and again at the so what is the solar cell center people are now looking into for solar cell as well as electronics there is a problem of natural radiation falling on the circuit okay and particularly if you are a satellite based circuits intense radiation is there so if you see the two comparison for radiation purpose there is a huge threshold shifts in the mobility degradation and therefore speed varies changes much more there can be huge power consumption change okay after before and after and there is what we call single event absent due to alpha particle hits if you look at analog now this feeling you know analog GUV this is British okay so analog functions are affected by here only small amount here everything is affected so if you have a analog block any open circuit sitting on and you are a satellite it will fail faster that is our worry it changes operating point changes bandwidth changes gain change offsets in stability what not then it also control biasing voltages are current and possible allows some compensation of radiation you can actually play with band gap references and feedback paths to compensate which is not possible in the digital some advantage some issues certainly not important issue that this figure is not here we will come back to that so basically what is analog circuit design has needs to consider in case of analog positive and negative signals both are required because generally it is a VDD minus VDD dual rails biasing is very important just now I showed within the gain range only you can keep the device so if you shift out there is no gain for you linearity is essential gain has to be constant so you are looking for that is why they are called linear circuits because they are constant gains we want in general any circuit but analog more less prone to noise because otherwise noise will supersede everything you want smaller change in parameters called drifts the problem as I say is there are no standard sets available blocks available we can use so you may have to either create your own and reuse it or design every time then very difficult right now is to design low voltage circuits and therefore no power circuits or maybe no energy circuits there are three parameters which we shall work in analog design these are our what you should say bread better parameters the trans conductance GM output resistance are 0 and the third and the most important input referred noise that is the three parameters important so as the game side is concerned outputs are concerned and finally for all analog circuit we are worried about bandwidths which is our so how do you tackle each of them and still do not lose on others is what the game is all about designs okay so we stop here today we will come back next time