Amplifier working proses


The basics of the operational amplifier. And within the upcoming videos, we'll talk more about this operational amplifier. and that we will see, how we will design the various circuits using this operational amplifier. So, as its name suggests, this op-amp is essentially an amplifier. and therefore the basic job of an amplifier is to amplify the input. Now, let's understand why it's referred to as the operational amplifier. So, in youth when digital computers weren't evolved, at that point the various mathematical functions like addition, subtraction, integration, and differentiation were performed using this operational amplifier. So, just by connecting a few resistors and capacitors, it's possible to perform the various mathematical operations. which is why this amplifier is understood because the p[rational amplifier. So, now if you see this circuit symbol of the operational amplifier, it is often represented by this symbol. So, it consists of two inputs and one output. And most of the operational amplifiers contain two power supplies. The positive and therefore the negative power supply.


 But there are many op-amp IC's which run on the only power supply. So, now during this operational amplifier, the input terminal which is marked by this positive sign is understood because the non-inverting input terminal and another input terminal which is marked by this negative sign are referred to as the inverting input terminal.And it'll get cleared to you very shortly why it's referred to as the non-inverting as well as the inverting input terminals.So, now if you see this operational amplifier, it is one quiet differential amplifier with a single output.It means this amplifier amplifies the difference between the 2 input signals.So, for instance, V1 and V2 are the input signals which are being applied to the present operational amplifier and for instance, the gain of this operational amplifier may be a, then the output is going to be equal to A times the V1 minus V2.So, for instance, if we've applied the single input to the present operational amplifier and we have grounded another input terminal that the output you'll get A times V1.Where A is that the open amplification of this operational amplifier.


The reason it's being referred to as the open-loop gain is that it's the gain of the operational amplifier when there's no feedback from the output to the input side.So, suppose if you're applying the sinusoidal signal up here, then at the output that sinusoidal signal should be get multiplied by the factor of this gain, and at the output,you should get the amplified sinusoidal signal.Now, here the phase of this output voltage will be equivalent because of the input voltage.Likewise, whenever we are applying an input to this negative terminal, and that we are grounding another terminal then the output of this amplifier will be adequate to minus A times the V2 because the difference between these two input terminals will be adequate to 0 minus V2, that's equal to minus V2.So, suppose for instance if we are applying the sinusoidal signal at the input then at the output we'll get the amplified sinusoidal signal which has a 180-degree phase concerning the input.


That means the output is going to get inverted by 180 degrees.And that is why this input terminal is known as the inverting terminal.Because the output is going to be get inverted with respect to the input.So, now here suppose if we apply the input signal between these two positive and the negative terminals then at the output we will get A times this differential input .Where here this A represents the open-loop gain of this operational amplifier.Now, this operational amplifier may be a very high gain amplifier.And the value of gain wont to be within the range of 10 to the facility 5, to the ten to the power6.So, let's say, albeit we apply the 1 mV of a signal between these two terminals, and let's say if the gain of this op-amp is 10to the facility 5, then at the output theoretically we should get 1 mV signal that's multiplied by the ten to the facility 5.That is adequate to 100V.Or for instance, if we apply 1V of a sign , then theoretically, we should always get the output as10 to the facility 5 volts.But that's impossible .And the output of this op-amp is restricted by the biasing voltages that are being applied to this op-amp.


So, the output voltage is going to be between these biasing voltages.So, if you see the voltage transfer curve of op-amp then it'll appear as if this.So, here this X-axis represents the differential input that's applied to the present operational amplifier.and the Y-axis represents the output voltage of the amplifier.And here the slope basically represents the gain of the amplifier, which wont to be in the range of 10 to the facility 5 to the ten to the power 6.Now, here for instance if the gain of the op-amp is 10 to the facility 6.And for instance, we are applying 1 microvolt a sign .Then at the output, we should always get 1V of a signal.Likewise, for instance, if we apply 10 microvolts of a sign , then at the output, we'll get10 V of output.But as we increase this input , then we will find that after some value of input signal, the output will get saturated to the value +Vsat, which wont to be but the positive biasing supply.So, during this way, as soon because the input voltage goes beyond some certain value, the output will be get saturated to the plus saturation voltage.And same is true for the negative input voltages.So, as soon because the input voltage goes beyond some threshold value at the output you will get minus saturation voltage.


So, whenever this operational amplifier is used in open-loop configuration that means there is not any feedback from the output to the input side, at that point albeit we apply small input between these two input terminals, then also you'll find that the output is going to be getting saturated towards the positive or the negative biasing voltages.So, this particular characteristic of the op-amp is especially useful once we use this op-amp as a comparator.So, are often "> this is often one among the applications in which this op-amp can be used.But if you see this op-amp, this op-amp can also be utilized in some other applications.Like, designing the active filters, oscillators,waveform converters, and analog to digital and digital to analog converters.And if we count the list, then the list will go on.

So, basically, this op-amp is extremely versatile and you'll find this op-amp in so many applications.Now, the rationale this op-amp is employed in so many applications is due to its different characteristics.So, let's examine the various characteristics of the op-amp due to which it's so versatile and it's getting used in several applications.So, before we see that let's examine the equivalent circuit of the op-amp.So, as you'll see here, this Ri is that the input impedance of this op-amp.Likewise, this Ro represents the output impedance of this op-amp.And the output voltage of the op-amp will be the open-loop gain multiplied by the difference between the input signals V1 and V2.So, now before we see the various characteristics of the op-amp, 

let's examine the various characteristics of the perfect op-amp.So the ideal op-amp should have this input impedance Ri that's adequate to infinity.So, that whatever input that's being applied between the input terminals will directly get applied to the op-amp.Similarly, the output impedance of this op-amp should be adequate to zero.That means whenever we are applying the output load to the present op-amp then the output voltage should directly encounter this output load.Then if you see the bandwidth of the ideal op-amp, the bandwidth of the perfect op-amp should even be adequate to infinity.It means it should support all the frequencies starting from the zero Hertz to the infinite.Similarly, the gain of the perfect op-amp should also be adequate to infinite.Apart from that whenever these two input terminals are zero, meaning the input to the present op-amp is zero, at that point the output of this ideal op-amp should be adequate to zero.Now, aside from these characteristics, there are few more characteristics of the ideal op-amp that's slew rate and therefore the common-mode rejection ratio.So, will see more about these different characteristics in detail in separate videos.But let's examine the fundamentals of these different characteristics.So, in a simple way, if I say, the slew rate is basically how briskly the op-amp is in a position to reach its final value.In that is especially useful once we are applying a square wave to the op-amp.So, for instance, we've applied the square wave to the input of this op-amp and at the output, we are becoming this output waveform.That is varying from zero volts to the V saturation voltage.So, the perfect op-amp should be ready to reach from zero volts to the Vsat volt in zero time.So for the perfect op-amp, the slew rate should be adequate to infinity.Generally, this slew rate is defined in the unit of Volt per microsecond.

That means how briskly the op-amp is able to answer the output voltage.Then there's another parameter, which is known because of the common-mode rejection ratio.So, let's understand very briefly what do we mean by this common-mode rejection ratio.We will talk more about it during a separate video.So, for instance, if we are applying the same input voltage to the present V1 and V2 then the difference between these two voltages is going to be equal to zero and at the output, we should always get zero volts.Likewise, once we are applying different input voltages V1 and V2 to the present op-amp then at the output the difference between these two voltages is going to be get amplified by a certain amplifier gain.So, this common-mode rejection ratio basically defines how well the op-amp is in a position to reject the common input voltages that are being applied to both its input terminals and the way well itis ready to amplify the difference between the two voltages.And it's generally defined because the ratio of differential gains divide by the common-mode gain.So, for the perfect op-amp, the worth of this common-mode rejection ratio should be equal to infinity.So, here is that the list of various ideal op-amp characteristics.

 So the ideal op-amp has infinite input impedance, zero output impedance, infinite open-loop gain, and infinite bandwidth and slew rate.And during this ideal op-amp, whenever the input is adequate to zero then at that point the output is also zero.And this ideal op-amp has an infinite common-mode rejection ratio.But if you see any practical op-amps, they used to possess finite input also because of the output impedance.Generally, this input impedance is in the range of megaohms, while the output impedance is within the range of few ohms.Similarly, the open amplification of the op-amp is not infinity but it wont to be within the range of 10 to the facility 5 to the ten to the power6.Likewise, for the sensible op-amps, when the input is adequate to zero, at that point also you will get some output at the op-amp.Generally, it wont to be within the range of a few. 

That is referred to as the offset voltage.And we will talk more about it within the separate video.So, here is that the list of various parameters and the values of various parameters for the general purpose 741 op-amp IC.So, now if you see the various op-amp ICs, they are optimized for the various parameters.So, for instance, if one op-amp is optimized for the very high slew rate, while another op-amp is optimized for the very high open amplification.And if you see another IC, you would possibly find that it's optimized for the very low offset voltages.So, depending upon your application you need to decide which parameter is critical for your application and support that you simply can decide which op-amp is suitable for your particular application.Now, thus far we've seen this op-amp in an open-loop configuration.That means, there was no feedback from output to the input.Now, within the next video, we'll see what happens when we offer the feedback from the output on the input side.So, I hope during this video you understand the different characteristics of this op-amp.So, if you've got any questions or suggestions let me know within the comment section below.