 In this lecture we will be continuing from where we left off in the last one where we had discussed the 2 products the receivers radio receivers AM and FM and the modem and AM and FM receivers only were discussed transmitters were not discussed whereas modem contains in a way if it is a wireless modem it will contain the same transmitter as well as receiver architecture right it will have modulator for transmitting and demodulator for receiving so that is special trans receiver architectural part that forms the front end of most of the PCs today. Now today's lecture will continue with the other 2 products that we had mentioned cell phone and ECG according. Now let us therefore consider first the cell phone I think this is one product which has now become so common that even the common man knows about the terminologies and the electronics a little bit of electronics that goes with cell phones that is the fortunate part we have educated by making the product become popular educated the public. So let us briefly go through the functioning of the cell phone the most dominant product of present day world most impressive performance in terms of utility and also misuse when utility becomes important it is also likely to be highly misused its basic function is to make and receive telephone calls over a radio link while moving around a widespread geographical area it connects to a cellular network this is a very basic concept that is a transmitter ok that is located near your area ok and there are such transmitters spread all around the city so that it is a cell like structure. So when one moves from one cell to the other the it smoothly changes over from one transmitter to the other transmitter. So this philosophy has been used in this cell phone trans receiver design they also support a wide variety of other services such as text messaging multimedia messaging email internet access short range wireless communications infrared and Bluetooth business applications gaming photography music play all these are special features of these cell phone. Mobile phones that offer these and more general computing capabilities are referred to as smartphones and the smartphone is now replacing almost all these computers and ordinary phones. So cell phone block diagram comprises of radio for transmission and reception is also part of it radio transmitter and receiver now we have the transmission occurring in analog domain most of the time and therefore communication occurs in the analog domain and it is conversion from digital to analog that takes place analog baseband ok and digital baseband we have classified it as from the analog it gets converted to digital. So this is the general architecture of a cell phone now this is block schematic indicating the analog front end and the analog back end with the digital signal processor primarily acting for collecting the digital information and also transmitting the digital information and the control signals ok allocating the control signals we have the front end we have a diplexer here actually transmission is done at one frequency and the reception is done at another frequency and this is the common unit which links it with the antenna both for transmission and reception. So we have tracing the path of the receiver just like any other receiver the RF front end here then the mixer converting the RF to IF this we had seen in the radio receiver also and it is the IF amplifier which is also a filter ok and that output is demodulated ok and that requires the help of a local oscillator which is tunable micro controller control is there to this to adjust the frequency corresponding to the RF that is getting received. So the baseband signal that gets generated here ok is going to the A to D converter here and then it is stored or displayed all those things are going to take place from this. Then on the other side whatever information that is stored or to be communicated that goes from the digital to analog for the modulator which also gets the help of local oscillator to convert it to the IF frequency and that is shifted to the RF that is required for transmission. So you will see that the front end remains almost exactly similar to what we had already discussed earlier. And here the micro processor controller also is interacting with the human interface as the switch board, dialing, memory and battery power control. So these are all the analog inputs that are given at this point for the micro controller ok. Now the digital thing is dealing with the baseband signal like speech, video and data ok. So you can see that this whole thing is the digital signal processing activity here including that of this. This is the typical fashion of the present day electronic system. The future electronic system will comprise of mainly digital signal processors helped by the analog front end and the analog back end which are also micro processor control and all the control signal comes from the lower frequency digital controllers. So this is the explanation for most of the thing that we have already mentioned RF front end. So typical part consists of a deep flexor a tunable band pass filter RF load transmitting power of cell phone is about 500 millivolts. RF filter in the transmission part is tunable and band pass filter. Antenna is connected to the transmitter and receiver through a deep flexor. Receive noise amplifier LNA it is normally called. This is in the other path receive path IF block. The output of the LNA goes to the mixer to generate an IF signal with the help of the local oscillator and is under the control of digital baseband processor to produce a sinusoidal signal at RF plus IF. The IF signal is amplified by IF amplifier which is fixed frequency band pass filter. IF amplifier output is demodulated okay and I think this is sort of omega RF okay minus the digital baseband is going to be at let us say the baseband frequency and it is facilitated by multiplying it with omega RF plus omega IF. The omega IF signal is amplified by IF amplifier which is a fixed frequency band pass filter. The IF amplifier output is demodulated using local oscillator which down converts the signal to analog or digital baseband. So analog back end and baseband the output of the demodulator may represent the digitally coded speech video or data. The video signal and speech signal are pre constructed using DTA converter. The digital data directly goes to the digital baseband processor. The output from the IF amplifier whose input is from the modulator is up converted to the radio frequency of transmission by a mixer and power amplified before getting connected to the transmitting. Speech and video signals generated by the user are converted into the digital data using A to D converters. Digital data goes to the modulator and to the digital baseband processor. So these are the functions of the various blocks of the cell phone. Now this is an important block power management. As you see that the most of the time in order to improve yield reliability in IC fabrication of these VLSI structures these are mainly made as single chip solutions okay. And power management in this single chip has to occur in terms of isolating the power supply for the digital primarily from the analog one. So that there is no interaction between analog and digital systems due to parasitic capacitive coupling or inductive coupling. So this kind of thing is made possible by efficient power management. Not only that efficiency of the system improves if we shut off those units that are not working at any one given time. So this also is managed by digital control. So basically nowadays all the analog systems that are necessary for an electronic system get controlled by the digital controller of the whole system right. So it is digital controlled analog subsystems. This is what we have to study. Now we come to the other important system health wise. Health monitoring has now become part of cell phone activity and so many things have been integrated into the cell phone that the future perhaps requires only the cell phone for most of our applications. Let us therefore look at the system that forms electrocardiogram is a non-invasive procedure for recording of electrical activity on the body surface generated by the heart. So ECG or EKG shows a series of waves that relate to the electrical impulses of heart beat that everybody knows now. So this is a typical pulse generated by the heart. This is called P this is QRS and this is T. It has features defined as P, QRS and T for each heart beat. The amplitude and relative timing of these various segments are used for diagnosis of any heart ailment. Important components of ECG heart rate that is the frequency about few hertz okay which means so many beats 40 to 300 beats per minute. P wave is of this frequency about few hertz again this is few tens of hertz QRS and T wave is again few hertz. High frequency potentials of the order of 100 to 500 hertz for more refined understanding of the ECG waveform. The other components which actually obstruct us from getting the complete ECG function correspond to the muscle activity which also is around the same frequency 5 to 50 hertz respiratory activity which is of very low frequency 0.1 to 0.5 hertz 8 to 30 beats per minute. External electrical noise this is the main enemy of the ECG capture 50 to 60 hertz EC mains. So most of the power line frequencies components which are close by also transmit this okay electromagnetic radiation and it dies off very fast okay because it is at very low frequency. However because of the power the strength that is picked up by the body is considerable. So we will depict this later on pictorially. Other typical electrical activity greater than 10 hertz muscle stimulators strong magnetic field pacemakers etc also interfere with this. That is a glimpse of what noise means in ECG recording. It uses several electrodes the primary thing is that it must be a differential pickup. So that the common mode noise voltage which is primarily 50 hertz line pickup gets cancelled simply because of the differential measurement. So this is a technique of putting the electrodes in such a manner that noise gets cancelled not filtered. The machine detects and amplifies the electrical impulses picked up by the electrodes that occur at each heartbeat and cause them onto a paper computer or any story that is the function of the ECG recording. So it simply picks up this okay and this is to be recorded in a paper or a computer are stored in a storage device. Now this is what you see as differential recording. This is very important in present day electronics. I would like to just highlight that the technology of IC fabrication has made a great impact in electronic circuits. What is it? The technology of IC fabrication has made us realize absolutely symmetric networks which means it is going to facilitate easy cancellation of common mode noise. This is the greatest thing that has happened in IC fabrication. This kind of thing never existed in discrete circuit fabrication. And this is how we get rid of the noise problem here by using a differential recording. So these are the two points okay and these two voltages are measured with reference to a common point okay and therefore the common mode voltage that gets picked up here hopefully okay it is very nearly equal and then gets cancelled. Obviously it is not possible that it is equal and therefore some amount of this 50 hertz noise still gets picked up because of the fact that these two points are okay not exactly having the same voltage with respect to this common point okay. So this has nothing to do with electronics but the electronic device that is going to be used as the front end here has to be a differential amplifier that is obvious to everybody. So that is the technique of noise cancellation differential recording between two points on the body armor they are defined as V1, V2 and V3 okay. So this is the arrangement of electrodes and you can see here get an idea of the signal the common mode noise that we are talking about this of the order of few volts 1.5 volts okay and the offset due to the electrode placement is of the order of 300 millivolts that is therefore going to pick up the 50 hertz noise and then the ECG signal is only of the order of few millivolts occurring at these frequencies. So this is the signal that we have to pick up earlier in the first lecture I had shown you how the ECG signal looks like with this predominant common mode noise that got picked up in spite of it being differential. Now these are the blocks that form the ECG so equipment we have a multiplexer here. So we place instead of just 2 sort of electrodes we place multiple set of pairs of electrodes to find the differential voltage at different points and multiplex this data and take an average okay and this is the best technique to eliminate noise as well as get a fairly good value of the actual heartbeat okay. Instrumentation amplifier is a differential amplifier which is an IC that we can fabricate it is a symmetric structure we will let us see and then we have a variable gain so as to adjust the output so as to make it compatible with that of the data converter that we are likely to use. After that we have the high pass filter low pass filter high pass filter to eliminate high frequency white noise mostly low pass filter to eliminate very low frequency noise which is interfering with the ECG and then notch filter to primarily to get rid of the 50 hertz or 60 hertz and then final amplifier only most of the amplification is concentrated here so that it is after all the removal of the noise that the signal gets amplified. Then it is processed after it is converted to the digital by the DSP and stored displayed or recorded. So this explains what I have just now indicated inputs from groups of electrodes are multiplexed and processed for the common mode rejection by the instrumentation amplifier the output of the INA is amplified and variable gain amplifier gain is adjusted so that output becomes compatible with that of the amplifier okay and the data converter. Frequency is below 0.05 hertz are eliminated by the low pass the high pass filter as a low pass filter and above 150 hertz are eliminated by the low pass filter and 50 hertz is eliminated by the notch filter. The output of the notch filter is amplified and coded to the digital form using A to D converter. The digital data is suitable for processing by a DSP for recording display or storage. Now we come to the basic analog signal processing functions that are required in all these functional blocks or gadgets electronic products that we have discussed amplification what does it mean attenuation or amplification. Mathematically this simply means okay multiplication by a constant this is multiplication by a constant alpha times let us say X X is the independent variable in this case voltage or current it does not matter. So if you can multiply alpha if alpha is less than 1 it is called attenuation it is called attenuation if alpha is attenuation if alpha is greater than 1 it is called amplification filtering that means getting rid of noise if it is within the band you will use what is called a notch filter if it is this is for within the band noise outside the band high pass low pass or band pass outside the band high pass filter low pass filter or band pass filter this notch filter is band stop filter these are the common filters that are used in most of the signal processing right what is therefore then comparing you are comparing either a voltage or current with a reference compare with the reference. Now this is nothing but a mixed mode circuit these are purely analog here the input is analog output is digital input is analog output this is for this multiplication it could be both analog okay then it is called modulator mixer and all that one analog one digital then it can act as multiplexer analog multiplexer it can select the analog signal that you want to input to the PC or something like that. So you give one analog comes you give zero nothing comes from that right. So when you actually apply zero to one analog you can apply one to the other analog okay so that other analog get selected that is what is called multiplexing. So multiplexer is a multiplier operation okay then both digital then it becomes an X or gate exclusive or gate. So these are the variety of mathematical operations that go with signal processing you can see a wide area of signal processing getting covered just by these operations. DTA conversion A to D conversion okay A to D we have already talked about this example of this is nothing but a comparator which is already discussed here there is a 1 bit A to D converter comparator is a 1 bit A to D converter D to A converter is nothing but sigma let us say A analog is equal to sigma 2 to power minus n V reference into AI I equal to 1 to n. So we have a n bit D to A converter so I ranging from 1 to n is nothing but a analog V reference is analog and this is digital a digitally controlled analog output you can get it is a multiplier again one input is analog another input is digital. So D to A converter can be treated as a multiplier where one input is analog and the other is digital just like multiplexer. So these are the basic things activities that get carried out and these are explained in detail further. So we see here the thing about amplification let us discuss this output is either a voltage or current in an amplifier since the variable can be voltage or current output can be available as a voltage or current then that is equal to K times input which is voltage or current plus some offset which is independent of input that is called an offset it can be a current offset or a voltage offset right depending upon what the output is. So the K has to be greater than 1 if it is amplifying if it is attenuating is less than 1. Now this becomes a control source okay voltage control current source voltage control voltage source so we have voltage control we have voltage control voltage source voltage control current source current control voltage source current control current source. So we have 4 combinations of the amplifier becoming possible theoretically there are no further amplifiers possible. So the basic definitions have to be understood very clearly first before we venture into any signal processing activities and this is the basic degree we have a voltage amplifier a current amplifier and then a trans conductance amplifier and a trans resistance amplifier that is possible theoretically with this kind of definition. Next it is important that you should be able to amplify a differential voltage that I have already indicated when we discussed about transducers that means it is not a single ended voltage amplification it is X1 and X2 as the 2 independent variables they may be V1 and V2 when they are voltages then theoretically any linear system will give you an output corresponding to X1 and X2. So that can be categorized as what is not wanted is that corresponding to X1 plus X2 by 2 this is called the common mode signal and X1 minus X2 this is called the differential mode signal this signal alone is important to be amplified in a differential setup and this signal has no place at the output. So the ideal differential amplifier or difference amplifier should give an output corresponding to only the difference X1 minus X2 however a linear system if it is designed then there will be output corresponding to both the inputs and they may not be equal if they are equal okay then it is a differential amplifier if it is not equal because of some mismatch because of non-symmetric because the circuit that is processing it is not exactly ideally symmetric then what happens is that this common mode signal appears and that is an error. And therefore output normally is proportional to the differential signal into some KD this is called the differential amplification factor and KC into X1 plus X2 by 2 which is the common mode signal and this KC should be ideally speaking in a symmetric structure that is amplifying it should be 0 in practice of course it is not 0. So where KD is known as differential mode gain and KC is known as common mode gain KD by KC is a measure of the quality of this difference amplifier. And that is measured by a parameter called rho this is called common mode rejection ratio it is normally expressed in terms of decibels as 20 log rho an ideal difference amplifiers should have common mode rejection ratio equal to infinity that is because KC should be 0 for it. So KD by 0 will correspond to infinity as far as rho which is called the common mode rejection ratio which is normally called CMRR CMRR these are again definitions that you should learn about before you understand the technology of fabrication of any active device or an amplifier. So we come to the important section on filtering you have all been familiar with coffee filters the same thing that electronic filter does it selects what you want to select right that is the liquid coffee as a liquid and the solid portion is retained. So same way the solid portion that is retained is the noise it should not come okay. So the liquid portion is what you want to accept and drink okay. So the signal bandwidth is the one that has to be permitting okay the signal to appear and reject the noise. So filter is for rejecting the noise and accepting the signal in areas bands of the signals. Filter can be as I pointed out earlier low pass to remove the high frequency noise high pass to remove the low frequency noise band pass to remove both low frequency and high frequency noise band stop okay to remove in band noise which is dominating when you remove the in band noise normally it so happens that you have to sacrifice some amount of information because it will also remove the wanted signal. Low pass filtering is going to be depicted this way ideal low pass filter is a box like approximate that is you do not want any component corresponding to frequencies beyond this okay. So above this bandwidth this is corresponding to the wanted signal bandwidth for example if it is audio and high fidelity music you want to collect then you would restrict it to about 20 to 30 kilo hertz that is the bandwidth over which you would accept the signal and reject this other high frequency signal okay. Now a non-ideal low pass filter that is what is practically realizable okay this is practically not realizable will give the reason later but for a single input you have multiple output possible. So anything that is having for single input multiple output possible is physically not realizable okay and therefore we have to approximate this filter to something better where for every input that is a unique output that is what is physically realizable and these filters for example are going to be the low pass filters that we will realize later using the available components. Now high pass filter that is we want to reject the low frequency noise. The low frequency noise corresponds to drift of a voltage because of temperature dependence mainly let us say or any temperature dependent activity results in this kind of okay drifting voltage and therefore that results in the offset voltage drifting all voltage or current and that has to be eliminated from the signal and that can be done by introducing what is called a lower cutoff frequency okay below this the noise gets eliminated and above this the signal is going to be passed. Now this is the box like approximation for a band pass filter the bandwidth of the signal let us say is corresponding to this for example this is an IF filter. So around let us say 455 kilo hertz maybe the center frequency is located and then the bandwidth corresponds to 20 kilo hertz on either side of the center frequency okay so that we want to receive high quality music okay. So 40 kilo hertz is the bandwidth and 455 kilo hertz is the center frequency we can design a filter not exactly having this characteristic once again it has to be approximated it can be better approximated by this kind of thing or in this case if you have a really troublesome neighborhood frequency that let us say this is what your cell phone is transmitting this is the neighborhood frequency okay where the power is more than if you design this kind of filter that power that will come into the your phone will be much more than your own power. So you will not be able to hear what your friend is talking okay but you will be able to hear the neighbors talk okay which is a noise right. So this is the trouble so what you do you kill that fellow right by introducing a zero of transmission here that means there is no transmission at all that is going to be received by you. So this filter okay can be realized later on we will see and therefore this particular transmitted power is killed here and here okay. So you look at this kind of zero of transmission okay wherever you have high power neighborhood frequencies interfering with your signal okay. Now same thing can be done for a band of frequencies here again this box like approximation is not accepted we will do an approximation of this okay either this way or this way to get rid of a band of frequencies okay now comparison. Comparison simply means like let us say we have an input voltage coming like this and this is the reference our comparator which may be a voltage comparator or current comparator as two inputs where this voltage is the incoming voltage and this is the reference voltage what happens to the output as long as let us say the input voltage is going greater than the reference voltage output goes negative it just gives let us say digital zero this is negative means let us say zero some voltage and if the input goes below the reference it goes positive. So as far as the output of this comparator is concerned it has only two states high and low okay that going from high to low or low to high occurs exactly at a voltage reference or a current reference depending upon the input chain this is something that is very very important in signal processing this converts the amplitude information to width information if you call this as duty cycle over a period then the duty cycle gets varied as this voltage reference is varied. So you can convert an amplitude information to width information this is called pulse width modulator okay this width information conversion is possible and this is having important application in DC to DC converters switch to more power supplies class 2 power amplifiers and this is a very simple concept to understand okay. Now we come to the last application that we are going to discuss that is multiplication the output of a multiplier is the product of two inputs let us say we are talking of voltage multipliers it can be current also where I naught is equal to K naught into I X into I Y here we have depicting we have depicted a voltage multiplier V naught is K naught into V X into V Y in precision multipliers this is made to work for plus minus 10 volts okay is therefore called a four quadrant multiplier plus minus 10 volts okay so this can work all the way from minus 10 to plus 10 for both these voltages and the maximum output of the multiplier itself is adjusted by adjusting K naught as 1 over 10 volts if you make this constant as 1 over 10 volts then output of the multiplier will never exceed 10 volts that is the standard precision multiplier design okay ICs are available for this kind of operation. So it is interesting fact that this is going to cover most of the communication applications the basic principle of which can be taught to anybody any engineer because the mathematics of this is very straight forward and simple. A non ideal multiplier will have a relationship obviously now V naught can be independent of both inputs that is called offset voltage it is having a component which has nothing to do with product of V X and V Y but only dependent upon one of the inputs V X or V Y these are called feed through components these also should be absent in an ideal multiplier. So K X has to be 0 K Y has to be 0 V offset also has to be 0 okay in an ideal multiplier in a practical multiplier these may not be exactly 0 these have to be adjusted to be 0 later on okay plus of course the non-linear components corresponding to V X square V X square and other non-linear higher order non-linear components can also exist by properly selecting the topology of the multiplier okay we can actually get the multiplier to be precisely this okay. Let us therefore see the application of this multiplier okay in communication. So I am taking the example of this multiplier now V naught is equal to K naught into V P 1 sine omega 1 T V X is V P 1 sine omega 1 T and other one V Y is V P 2 sine omega 2 T. So then what happens output is K naught V P 1 V P 2 by 2 cos A minus B omega 1 minus omega 2 T okay this is not plus actually it is minus cos omega 1 plus omega 2 T okay. So this is called double side band you can see two side bands omega 1 minus omega 2 omega 1 plus omega 2. So this is what is called double side band okay modulator balanced modulator it is called and mixer. So this may be the RF this may be the RF plus IF and this is RF then you will get the difference components which corresponds to IF that is how in the mixer you get the IF and this one will correspond to then this twice omega RF plus omega IF okay. So it is a higher frequency component by using a band pass filter that is IF filter you can select this and reject this that is the operation of the mixer that is finished right. So V naught is equal to K naught into V P 1 sine omega 1 T and V P 2 sine omega 2 T into that is nothing but demodulated DSB. You multiply it again the modulated DSB modulated output is V X and V Y corresponds to sine omega 1 T okay. Then what happens you get here okay K naught into V P 1 into V P 2 by 2 into 1 minus cos 2 omega T because that is because this is sine squared omega 1 T which is 1 minus cos 2 omega 1 T by 2. So you get rid of this higher frequency component by using a low pass filter okay then you will get an output okay which is a sort of DC okay that is the modulating frequency component. So this is a demodulator omega 2 is the modulating frequency component you get that base band signal. So this is the down converter or this is the base band signal extractor demodulator what it is called DSB demodulation. So you can see that the same multiplying function depending upon the input acts as a mixer or a demodulator. Now if they are of the same frequency if omega 1 is equal to omega 2 they might have a phase difference. So this is sine omega T this is sine omega T plus phi then what you get you get K naught V P 1 V P 2 by cos phi the difference and sum 2 omega T plus phi this can be got rid of by using a low pass filter and you get a DC dependent upon the phase shift. So this is known as phase detector if you get rid of this if you get rid of this then what remains that is by using a high pass filter okay you can get rid of the low frequency that is DC and select this and then this is a frequency doubler right. So this same structure acts as a phase detector a frequency doubler that means from omega you can get 2 omega from 2 omega multiplied by another omega you can get 3 omega. So you can generate all the harmonics by using this process of multiplication. So it is used for frequency synthesis right. So it is a powerful unit this process of multiplication is a powerful unit for obtaining most of the communication functions okay except for linear that is amplification okay. If you actually make one of the voltages DC it becomes a voltage controlled this is a VCA what it means is VX is let us say VC okay then what happens output is K naught VC into V P 2 sine omega T. So you get the signal V P 2 sine omega T getting amplified by this factor and you can vary this by changing VC. So it is a voltage controlled amplifier okay used in music synthesis and all right. So this is one of the most powerful IC that can be understood okay by anybody and used in practical laboratories to understand the basic communication principles. This is what we have already explained digital to analog conversion right. So the input is a N bit digital data and output is an analog signal output. So we have this as sigma of I equal to 1 to N AI 2 to power minus N you reference where AI is either 1 or 0. So that is nothing but the output of a N bit digital data. It can also analog output of a N bit digital it can also be called a multiplier with V reference as analog input and A1, A2, AN this is digital word is the digital signal. A to D converter the output is a N bit digital data and input is an analog signal a comparator is a 1 bit A to D converter okay a comparator is normally represented as a voltage or a current comparator. Now signal generation you come to again one of the basic principles which you have studied in your plus 2 okay this second order harmonic equation it is called del squared V instead of why I am using V here voltage del T squared plus KV equal to 0. This is second order differential equation with first order term being absent this is called the harmonic oscillator equation with all of you have studied in your plus 2. The solution of this differential equation V is equal to VP sine root of K into T plus phi omega is equal to root K is the radian frequency at which this will give an output a sinusoidal output. The phi and VP depends upon the initial conditions. So this is the basic principle used in generating any sine wave in electronics also this principle is used okay. So all our sine wave generators which are needed for test oscillator simulation so these are generated by simulating this equation. So any system that generates sine wave has to simulate this equation. So power supplies power supplies form the last part of the subject but the most important part also. So here we are going to be dealing with switch the power supplies which are the most efficient power supplies okay and they reduce the size of the component parts to such an extent because of the high frequency of switching and we have also what are known as low dropout regulators okay which are most important topics to be discussed in power supply design okay. These are purely analog. However these are going to be controlled in power supply management which is an important part of system design. So power supply management is an important part of power supply design which is going to be done digitally. So microcontrollers and DSPs can be therefore used efficiently to control the power supply so that efficiency of the whole system is maximum. So we have in conclusion discussed the cell phone architecture and the ECG architecture wherein all these four products that we have discussed emphasize one point. The communication is always carried out in analog and communication in future may occur within the chip just forget about outside the system right. Outside the system communication is already happening in analog in terms of podiums being used in terms of RF front end being used and therefore communication outside the system domain has already come into existence in analog. Communication is likely to take place within a digital system itself to talk to various digital blocks which are occurring in the system. The wired connection or the line connection okay is going to be becoming denser and denser and therefore it will be ultimately wireless connection within the chip most probably is the trend of future. So analog has to be learnt that is no way out so let us learn this okay in the future lectures the basic principles of analog signal processing is going to be emphasized from system design view point. What are the analog systems that can be realized using these basic blocks that we have already emphasized right. So the IC design which will involve the transistor may be MOS today okay is going to be a higher level course very few offers are going to be involved in IC design just like DSP design is going to be done by very few people but DSP usage has to be learnt by every engineer today right likewise understanding analog ICs and usage of analog ICs is something that everybody has to understand first before sort of specializing in IC design this kind of turn is going to be beginning of understanding VLSI.