Difference between Inverting and Non-inverting Amplifier

The term Op-Amp or operational amplifier is basically a voltage amplifying device. It uses exterior feedback components between its inputs as well as output terminals like resistors & capacitors. An ideal operational amplifier has different characteristics which include the gain of open-loop is infinite, the input resistance is infinite, o/p resistance is zero, offset is zero and high BW. An op-amp includes three terminals namely two inputs and one output. The two input terminals are inverting and non-inverting whereas the third terminal is output. These amplifiers are widely used to execute mathematical operations and in signal conditioning because they are almost ideal for DC amplification. This article discusses the main difference between  inverting and non-inverting amplifier

What is the Inverting and Non-inverting Amplifier?

To know about what are inverting and non-inverting amplifiers, first of all, we have to know its definitions as well as differences between them. The difference between these two mainly includes the following.

What is an Inverting Amplifier?

In this type of amplifier, the o/p is precisely 180 degrees out of phase to input. When the +Ve voltage is applied to the circuit, then the o/p of the circuit will be –Ve. The circuit diagram of the inverting amplifier is shown below.

Inverting-Amplifier
inverting-amplifier

Once this amplifier is assumed as an ideal, then we have to apply the virtual short concept at the i/p terminals of the op-amp. So the voltage at the two terminals is equivalent.

Apply KCL(Kirchhoff current law) at the inverting node of the amplifier circuit

(0-Vi)/Ri + (0−Vo) / Rf = 0

By simplifying the above terms we will get the following formula.

Voltage gain (Av) = Vo/Vi = –Rf /Ri

The gain of the inverting amplifier is Av = –Rf /Ri

What is the Non-inverting Amplifier?

In this kind of amplifier, the output is exactly in phase to input. When a +Ve voltage is applied to the circuit, then the o/p will be positive. The o/p is non-inverted in terms of phase. The circuit diagram of the non-inverting amplifier is shown below.

Non-inverting-Amplifier
non-inverting-amplifier

Once the op-am is assumed as an ideal then we have to use the virtual short concept. So the voltage at the two terminals is equivalent to each other.

Apply KCL at the inverting node in the circuit

(Vi−Vo)/R2 + (Vo−0)/R1 = 0

By modifying the above terms, we can get the following formula.

Av (Voltage gain) = Vo/Vi = (1+Rf/Ri)

The gain of a non-inverting amplifier is Av = (1+Rf/Ri)

Difference between Inverting and Non-inverting Amplifier

Inverting Amplifier

Non-inverting Amplifier

The type of feedback used in this amplifier is voltage shunt or negative feedback. The type of feedback used in this amplifier is voltage series or negative feedback.
The input & output voltages of this amplifier are in phase The input & output voltages of this amplifier are out of phase
The output of this amplifier is inverted. The output of this amplifier is in phase by the input signal.

 

In this amplifier, the reference voltage can be given to the inverting terminal

 

In this amplifier, the reference voltage can be given to the non-inverting terminal

 

The gain of this amplifier is Av= – Rf/Ri The gain of non-inverting amplifier Av= (1+ Rf/Ri).
The i/p resistance decreases because of the –Ve feedback. The i/p resistance increases because of the –Ve feedback.
The voltage gain of this amplifier can be altered when less than, greater than or equal to 1 The voltage gain of this amplifier is >1
The i/p impedance is R1 The i/p impedance is very large

FAQs

1). What is the inverting & non-inverting amplifier?

The amplifier which has 180 degrees out of phase output with respect to input is known as an inverted amplifier, whereas the amplifier which has the o/p in phase with respect to i/p is known as a non-inverting amplifier.

2). What is the function of the inverting amplifier?

This amplifier is used to satisfy barkhausen criteria within oscillator circuits to generate sustained oscillations.

3). What are noninverting amplifiers used for?

Non-inverting amplifiers mainly used where high i/p impedance is needed.

4). What is the function of the non-inverting amplifier?

It is used to provide a high input impedance

5). Which feedback is used in the inverting amplifier?

This amplifier uses -Ve feedback to precisely control the amplifier’s gain, however, causes a drop within the amplifiers to gain.

6). What is an inverting input?

An op-amp has three terminals like two inputs & one output, where one of the input is known as inverting input and it is marked with a minus (-)

7). What is the voltage gain of an inverting amplifier?

Voltage gain (A)= Vout/ Vin = – Rf/Rin

8). What is the voltage gain of the Non-inverting Amplifier?

Voltage gain (A) = Vout/ Vin = (1+ Rf/Rin)

9). What is the effect of negative feedback on the non-inverting amplifier?

  • Input impedance will be increased and the output impedance will be decreased.
  • Bandwidth will be increased
  • Output noise of the amplifier will be reduced
  • The impact of noise will be reduced.

Thus, this is all about the difference between the inverting and non-inverting amplifiers. In most cases, an inverting amplifier is most commonly used due to its features like low impedance, less gain, etc. It provides signal phase shifts for signal analysis within communication circuits. It is in the implementation of filter circuits like Chebyshev, Butterworth, etc. Here is a question for you, what are the applications of inverting & non-inverting amplifiers?

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