[Music] hello everyone i am krishna gupta i am assistant professor in electronics and communication engineering in ajay kumar gurg engineering college gaziabad i am going to take the classes of the subject analog circuits so today is the first lecture this is the first lecture of for analog circuits in this particular class i am going to discuss the basics of analog circuits what is analog what is digital then about amplifiers then will give you the introduction of the complete subject so i will start with the introduction then will come to the analog versus digital then after that amplifier then after that we will discuss about the complete subject what we are going to learn in this subject analog circuits so starting with the introduction to analog circuits basically this analog word it is uh very much popular we know that what is analog we we we hear it in our daily life in fact we all are surrounded with the analog systems we all are surrounded with the analog system everything is analog around us like what i am speaking its analog what you are hearing that is analog what we smell that is analog so everything around us is analog then the question arises that if everything around us is analog then as we hear that ah the world is going to disturb fine so if the world is going to dis digital then why we need analog fine so its a very simple the real world data is analog fine so we have to deal with analog we cannot escape it and further and of course the computer is your digital the computer is disturbed it will only understand the digital signals right so whatever analog signals we are dealing with we have to convert this analog signal into digital signal with the help of analog to digital converter fine so this analog there are various example of analog and digital like in analog we know that it is a continuous in nature its a continuous in nature and the digital that is discrete in nature fine so one example of analog system and digital system is like thermometer we all use this thermometer in our daily life fine so two kinds of thermometer we study in our daily life we use in our daily life one is your mercury thermometer mercury thermometer so what happens in mercury thermometer when we touch this mercury thermometer to the body then the level of the mercury rises fine and we just note down that reading of the temperature it may be one zero one degree fahrenheit ah it may be one zero two it may be one zero three five that is in mercury thermometer but in digital thermometer what happens in digital thermometer in distal thermometer we get the reading like this one zero one one zero one point one one zero one point two one zero one point three and so on fine so if the body temperature is one zero one one zero one point one one zero one point two anything but it may happen that the body temperature may be one zero one point one five one zero one point one five it may be one zero one point two five so with the help of digital thermometer we cannot measure one zero one point one five one zero one point ah two five right we cannot measure that but with the help of mercury thermometer we can measure one zero one point one five one zero one point two five but yes of course we need more focus we need more concentration to read that reading 101.15101.25 but yes with the help of mercury thermometer we can we can measure 101.15101.25 but with the help of digital thermometer what happens the values are discrete the digital thermometer will give you the value of one zero one or one zero one point one one zero one point two but not in between one zero one point one and one zero one point two fine so this mercury thermometer is your analog thermometer this mercury thermometer is the analog thermometer and this is your digital thermometer this is one example which i have given and this thermometer we use in our daily life now coming to next that is amplifier so amplifier it is a very popular element very crucial element very important element of analog circuit so as the name suggests this amplifies the signal the function of the amplifier is it converts weak signal into a strong signal weak signal into strong signal that is the function of amplifier so obviously the question arises that why we need to convert weak signal into a strong signal the reason is the sensors which we are using in our daily life it produces electrical signal right like temperature sensor it senses the rooms temperature and it converts that temperature into some electrical quantity fine so that electrical quantity that electrical quantity which we we are getting from the sensor that is very small in magnitude that may be in millivolt or in microvolt so the strength of the signal it is very small it is very small so it is very difficult to process such a small strength signal that is why we need to amplify this small signal that is the first reason that is why we need amplifier and another important reason is effect of noise effect of noise so if your signal strength is very less then it can be easily corrupted it can be easily corrupted by noise and if we are designing electronic circuit there will be noise due to that register transistors because of the random motion of electron that voltage is generated and desired voltage is generated that is your noise voltage so it will be there it will be there so that noise voltage can corrupt your this signal electrical signal generated by the sensor so that is undesired if this signal is corrupted that means your information will be lost that is not acceptable that is not acceptable we do not want to lose our signal to lose our information so we need to amplify this small signal generated by the sensor once it is amplified then the effect of noise it will be very very less that is the need of amplifier and if there is a sensor and of course in that case we need amplifier along with sensor we need amplifier because the signal generated by the sensor it is a very small in strength it can be easily corrupted by noise so i am discussing this point need of amplifier so as i have discussed that this amount of noise which is generated in the circuit it should not corrupt your signal sensed by the sensor that is very important so we need to increase the value of the voltage and we need to increase the value of the voltage such that your noise it should not corrupt your information fine one example is your microphone fine like caller mic fine so what is doing what i am speaking that is the sound signal it creates a pressure and that sound signal is further converted into electrical signal but that electrical signal generated by the microphone it is very small so we need a battery operated amplifier that is your amplifier that amplifies the signal generated by the microphone that is the example of amplifier fine along with microphone we connect to amplifier fine so that is one example of amplifier and further with the help of these amplifiers we will study that we can design oscillators we can design filters we can design analog to distill and distill to analog converters so this this is very basic why we need amplifier but it is not only limited to this like it it not only removes the it not only combat the effect of noise but also it can be used in various applications in analog design now next question arises as i said that amplifier it converts weak signal into its transitor so which parameter is amplified actually amplified when we say that amplifier is amplifying the signal so there are three parameters one is voltage another one is current and the third one is power fine so which parameter actually the amplifier amplifies whether it is voltage current or power we can understand it with the help of transformer we all family we are we all are familiar with the transformer like step up transformer in step up transformer what happens if there are turn ratios ah it is if a one s to n right the turn ratio is one is to n this is your primary this one is your secondary and if we apply a signal v m cos omega t at the primary so what will be the voltage appear at the secondary since the number of turns at the secondary is n so the voltage at the secondary it will be n into v m cos omega t so see your step up transformer it is amplifying your voltage it is increasing the level of voltage but can we say that it is an amplifier we know that in transformer if voltage is increased by the factor n then your current is reduced by the factor n so the point is that if we calculate the v dot i product that is power at the primary and v dot i product at the secondary then both the power it will be same because at the secondary what is happening if voltage is increasing then current is decreasing and vice versa also if we want to increase the current level just reverse this turn ratio and s21 make it make it ns21 it will increase the level of current then but in that case the voltage will be reduced so ultimately v dot i product will be constant if v dot i product is constant so your power is considered your power is not amplifying so this transformer it is not an amplifier it is not an amplifier fine so the amplifier amplifies the power the power level should boost up only then we say that it is an amplifier if it is only about voltage or current then your transformer can also it can increase the level of voltage and current but it is all about power now next one is this question arises that this is your amplifier and if we are giving the power p in to this amplifier and we are getting the power p out from this amplifier so as per conservation of energy your p out cannot be greater than p in then how this amplifier boost up the power obviously that conservation of energy is it is applied everywhere it is applied here also fine so how this conservation of energy equation is balanced we know that the amplifier needs some dc battery that is your suppose that vdd supply voltage is there dc supply voltage is there so this amplifier from where it is getting power from one source the one source is your supply voltage the one source is your supply voltage the amplifier is getting power from the supply voltage another source of power is your input signal signal source which we have connected to the amplifier at the input side fine so if this power is pl that is the power drawn from the supply then the total power taken by the amplifier it will be p l plus p and of course it will be equal to your p out plus obviously some power will be lost inside the amplifier so that is your we can say that dissipated power fine so this equation will be balanced fine so actually your input signal strength is increased obviously the conservation of energy is applied and that equation is balanced with the help of this battery this battery fine so amplifier amplifies the power next one is types of elements this is very basic you all are familiar with it and we are going to use these elements to design analog circuits so like active elements we know that which can amplify for example your transistor in transistor mainly we are going to study bjt and mosfet bipolar junction transistor and mosfet that is field effect transistor metal metal oxide semiconductor field effect transistor that is mosfet fine passive elements you know that resistor inductor capacitor it cannot amplify passive element cannot amplify the signal to amplify the signal we need active element linear elements like your register resistor is a linear element non-linear element like your diode and transistor diode and transistors are non-linear element fine so these are the just basic introduction of active passive linear and non-linear so just we we are going to design the circuit with the help of these elements next one is discrete circuit versus integrated circuit so discrete circuit as the name suggests we require some discrete components like register capacitor inductor diode transistors and we design that circuit on a breadboard we design that circuit on breadboard or pcb that is your discrete circuit like you do in your laboratory right if you need to design an integrator or differentiator circuit or any filter you take some components and you design that circuit on breadboard and pcb that is your discrete circuit integrated circuit is that is in short it is called ic we design the circuit on a single chip that is a silicon wafer and it's a long process i see designing is a long process right so you have seen that i see in your laboratory like seven four one i see triple five timer i see your gate ics mux ics etcetera fine so in analog circuits mainly we are going to deal with discrete circuits fine whatever circuit we are studying in we are going to study we are going to learn in analog design we can implement it on breadboard fine mainly it is about discrete circuit fine but there are various advantages of integrated circuits like ah the area occupied the area occupied by ic is less the power consumption of ic is less and obviously the speed is higher and the reliability of ic is more also the reliability is another factor because when we design discrete circuit there are a lot of soldering and that soldering can break so the reliability can affect in discrete circuit but ics are more reliable but of course for every small work we cannot go for ic it's a long process it it it may be costly also in some cases because if the ic is not easily available in the market then the cost will be high it's a long process in fact so we cannot go for ic for every small application sometimes of course this discrete circuit is very very very very very helpful it is very helpful fine so so this is about the subject of analog circuits in unit one we are going to firstly study diode circuits then about transistors then biasing then small signal analysis of those amplifiers to calculate different parameters like input resistance output resistance voltage gain etcetera then different configurations different configurations like in bjt common emitter common base common collector in mosfet there are three configurations common source common gate common train so it is not like that these are the only topics in analog these are the few topics of analog circuit which i am going to just give you a small overview right in unit 2 we are going to learn frequency response of common meter and common source amplifier that is the low frequency response high frequency response how the how the performance of amplifier is affected at low frequency at high frequency that we will learn in frequency response then different feedback topologies then we will learn about stability also like when the circuit is stable when the circuit is not stable fine then in unit 3 we are going to learn oscillators unit 3 is all about oscillators oscillator is a device which is used to generate a signal of a particular frequency you all have seen these oscillators in your laboratory like function generator you can generate a sine wave you can generate a square wave you can generate triangular wave right so we will learn about oscillators in unit three that is also the kind of feedback we use positive feedback in oscillators we use negative feedback in amplifiers so negative feedback we will study in unit 2 and positive feedback we will study in unit 3 then in unit 4 we will study a very important component of analog design that is current mirror that is very helpful to bias the circuit it is also used as a active load that helps in increasing the gain also then another kind of amplifier that is your differential amplifier right then lastly unit 5 in unit 5 another kind of amplifier that is your operational amplifier operational amplifier so it is basically a difference amplifier so we will see the beauty of this op-amp in short it is called op-amp that is operational amplifier it can be used in many applications we can we can use this operational amplifier to design various circuits we can perform various operations like we can design summer circuit subtractor circuit we can design integrator differentiator we can design log amplifier anti log amplifier multiplier divider with the help of operational amplifier that is the that is a very important element of analog with the help of this op-amp we can design various circuits and with the help of this op-amp we will further design filters we will further design filters and the filters which we we will learn in unit 5 this is active filters this is active filter not passive active filter means along with passive elements along with passive elements we will use some active element that is that may be transistor mostly we use op-amp because operational amplifier ic one of the ic 741 ic it is easily available it is very cheap also so with the help of 741 ic we can design active filters fine so all these things we are going to study in the subject analog circuits along with it see there are few other topics also that we will learn in upcoming classes so this is just the in the introduction class about what is analog what is a digital and what is amplifier what does this amplifier amplifies why we need amplifier because amplifier is very important element and with the help of amplifier you will see that we can design oscillators we can design ah filters right we can design adc dacs and so there are various applications so it is very important to understand the amplifier in analog design okay so this is all about this class in the next class i will discuss about diode circuits thank you you