# Non-Inverting Op-Amp and Op-Amp as Buffer

Hey friends, welcome to the Kohiki Blog ALL ABOUT ELECTRONICS. So in this article, we are going to talk about the non-inverting op-amp configuration and we will see how to use this op-amp as a voltage follower.

Now in the last article, we had seen the inverting op-amp configuration and in that configuration, we had seen that using the negative feedback we can control the gain of this op-amp. And in that configuration, we have applied the input to this inverting terminal of the op-amp and we have grounded the non-inverting terminal. Now let us see what happens when we apply this input to this non-inverting terminal.

## Non-Inverting O-Amp Configuration

• So let’s say we have applied the input to this non-inverting terminal and we have grounded this inverting terminal.
• So, this kind of configuration is known as a non-inverting op-amp configuration because here the output and input are in a phase.
• so now for this configuration let us find the relation between this output and the input voltage. so now before we find the relationship between the output and input voltage let me redraw the same circuit so that you can have a better idea about the circuit.
• So here I have redrawn the same circuit in a different way. So here we have applied the input to this non-inverting input terminal and we have a feedback resistance Rf between the output and the inverting input terminal.
• if you see here the one end of this resistance R1 is connected to the resistance Rf and another end of this resistor R1 is connected to the ground. So if you see here the fraction of output voltage is going as feedback to this inverting input terminal.

## Derivation of Closed Loop Voltage gain for Non-Inverting Op-Amp Configuration

So let us say here at this point the voltage is Vx and this Vx voltage is going as feedback to this inverting input terminal. Now using the voltage divider rule we can say that this voltage Vx is equal to R1 divide by R1 plus Rf into Vout. So this voltage will be going as feedback to this inverting input terminal. so at this point also the voltage will be equal to Vx.

• Now in the last article, we had seen that whenever we are using this op-amp in a negative feedback configuration then there will be a virtual shot between both the input terminals of this op-amp. It means that whatever voltage appears at one end of this input terminal, the same voltage will appear at the other end of the input terminal.
• It means that V Plus is equal to V minus and that is because of this virtual shot between this non-inverting and the inverting input terminal.
• So here in this configuration, we are applying the input voltage to this non-inverting terminal that means V Plus that is equal to Vin so because of this virtual shot at this inverting input terminal also the voltage should be equal to Vin, which means V minus should be equal to Vin. And we know thatV minus that is equal to Vx.
• So we can write this input voltage Vin that is equal to R1 divide by R1 plus Rf into Vout. Or we can say that V out divide by Vin that is equal to R1 plus Rf divide by R1. That is equal to 1 plus RF divide by R1. So this will be the closed-loop gain of this non-inverting op-amp configuration.

## Advantage of Non-Inverting Op-Amp configuration over Inverting Op-Amp configuration

• So in a non-inverting op-amp configuration, the relation between the output and input is equal to 1 plus RF divide by R1.
• So in this non-inverting of op-amp configuration also just by controlling the value of this RF and R1, we can control the gain of this op-amp. But in this non-inverting op-amp configuration, the output and input will have the same phase.
• so let’s say if I apply 1 volt of DC signal at this non-inverting input terminal and if I take the value of R 1 as 1-kilo ohm, then my gain of this op-amp will be equal to 1plus 2 divided by 1, that is equal to 3.
• So at the output, I will get 3 volts of DC signal. Or instead of DC voltage let’s say if I apply a 1 volt of sinusoidal signal and if I have a value of RF as 2-kilo ohm and R1 as 1-kilo ohm then at the output I will get a 3 volt of amplified AC signal which is having the same phase with respect to the input signal.
• So in this non-inverting op-amp configuration just by controlling the value of this feedback resistance RF and R1, we can control the gain of this op-amp and in this configuration, the output and input are in a phase.
• so this is all about the non-inverting op-amp configuration. so now here the question is what is the advantage of this non-inverting op-amp configuration over this inverting op-amp configuration because if you see both the configurations in both the configurations we can control the gain using this feedback resistance RF and R1.
• so let us find out some of the advantages of non-inverting open configuration over this inverting op-amp configuration. Now one of the obvious advantages of this noninverting open configuration is that the output and input both are in a  phase. while in the case of this inverting op-amp configuration, there is a 180-degree phase shift between the output and the input voltage.
• Apart from this, if you see this non-inverting op-amp configuration then in this configuration the input impedance of the circuit is very high and if we consider the ideal op-amp then, in that case, the input impedance of the circuit is infinite. While in the case of this inverting op-amp configuration, the input impedance depends upon the value of R1.
• So if we consider the ideal op-amp, then in that case the input impedance of this inverting op-amp will be equal to R1. So now let us derive the expression for this input impedance in case of this inverting as well as the non-inverting op-amp configuration.

## Input Impedance of Inverting Op-Amp

So now if you see the inverting op-amp configuration then in this configuration the input impedance is the impedance that is seen through this voltage source Vin or in another word we can say that the input impedance of this configuration is equal to the input voltage divided by the current that is going into the circuit. So let us say the current In is going into this circuit.

• So now here the ratio of input voltage divided by this input current will give us the input impedance of this configuration. now we know that in this inverting op-amp configuration, this node will act as a virtual ground because here this non-inverting terminal is already grounded.
• so we can say that this In is equal to Vin divided by R1. Or we can say that R1 is equal to Vin divided by  I in. Now we know that V is divided by In is equal to input impedance.
• So we can say that the input impedance of this inverting op-amp configuration is equal to R1. so the input impedance of this configuration depends upon the value of R1. so let’s say if the value of RR is very low then in that case the input impedance of the circuit will be low.

## Input Impedance of Non-Inverting Op-Amp

so similarly let us find the input impedance of this non-inverting open configuration. So in this non-inverting op-amp configuration also the input impedance is the impedance that is seen through this voltage source Vin. So let us once again assume that the current that is being supplied by this voltage source is Iin.

And the ratio of this V in divided by I in will gives us the input impedance of this non-inverting op-amp configuration. So now if we consider this open as an ideal op-amp then there will not be any current that is going into this inverting and the non-inverting terminals.

• we can say that this input current Iin is equal to approximately zero and hence we can say that the input impedance is equal to infinite.
• so now in any circuit whenever we have a very high input impedance then that will ensure that the source that is connected to that circuit will not beget loaded.
• so let us understand this point. so let us say we have one voltage source Vs and it is having source resistance RS. And it is connected to one circuit, and this circuit has an input impedance Zin.
• so now whenever the value of this input impedance is comparable to the value of these Rs then, in that case, the voltage that appears across the two terminal of the circuit will be equal to Z in a divide by Zin plus RS into V s. And as Zin is equal to RS then the value of voltage V will be equal to Vs by 2.
• so only half of the voltage will appear across this circuit. so in any circuit, the value of input impedance should be very high, so that whatever voltage that is being applied to that circuit will entirely appear across that circuit. so in this case of non-inverting op-amp configuration, as the input impedance is approximately equal to infinite or in practical case itis very high so whatever voltage that is applied to that circuit will entirely appear across that circuit.
• so that is the advantage of this non-inverting open configuration. Now in this non-inverting op-amp configuration, let us say we have Rf that is equal to 0 and R1 that is equal to infinity. Then the circuit will look like this. so this circuit is known as the open as a voltage follower circuit or opens as a buffer.

## Op-Amp as Buffer (or Op-Amp as Voltage Follower)

so here we have shorted this output terminal with this inverting open terminal. so at this point voltage will be equal to Vout and because of the feedback V minus that is equal to V plus or we can say that because of the feedback we have a virtual shot between this inverting and the non-inverting op-amp terminals.

• so we can say that V minus will be equal to Vin, or we can say that Vin will be equal to Vout.  so it means that whatever voltage is applied to this non-inverting op-amp terminal, the same voltage will appear at the output of this op-amp.
• So we can say that the output voltage follows the input voltage and that is why this circuit is known as the voltage follower circuit.
• So the characteristics of this circuit are that the input impedance of the circuit is very high or ideally it is infinite and the output voltage will be equal to the input voltage.
• so because of these two characteristics, this circuit is also known as the buffer circuit because it will pass whatever input that is coming to it as it is and it will provide a very high input impedance.
• So using this buffer circuit, we can isolate the two different circuits and at the same time we can ensure that whatever voltage that is appearing at the output of one circuit will appear at the input of another circuit, and that is particularly useful when we have a low input impedance in one circuit.
• So I hope in this article you understood the non-inverting op-amp configuration and the advantages of this non-inverting op-amp configuration over the inverting op-amp configuration and how to design the voltage follower or the buffer circuit using this op-amp.

### Derive the equation for output voltage for non inverting amplifier with necessary waveforms ?

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### 741 op amp is an example of ___ opamp

The 7400 series is followed from way back. These are literally created mistreatment TTL logic currently they’re being replaced by CMOS logic.
We see 2 letters at the start of the IC range. It really suggests that the corporate that has factory-made it. for instance, a metallic element stands for Lone-Star State instruments.
Two digits, wherever “74” denotes an advert temperature vary device and “54” denotes a military temperature vary. traditionally, “64” denoted a passing series with associate degree intermediate “industrial” temperature vary.
For the city question, I even have 2 reasons. 2 numbers seventy-four area unit as mentioned higher than. one is chosen as a result of it contains just one op-amp. as a result of in LM324, it’s four op-amps. the opposite reason may well be as a result of it’s the primary op-amp free within the market by Fairchild company.
It consists of 2 inputs associated with degree 2 outputs, particularly inverting and non-inverting terminals. this 741 IC is most typically employed in numerous electrical and electronic circuits. the most intention of this 741 op-amp is to strengthen AC & DC signals and for mathematical operations.

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