# Inverting Amplifier – Applications

An inverting amplifier is an operational amplifier circuit which produces amplified output that is 180° out of phase to the applied input. Inverting amplifier is also known as inverting operational amplifier or inverting op-amp.

Contents

## Inverting operational amplifier

Figure 1 shows the basic inverting operational amplifier. The input signal Vi is applied to the inverting terminal through the R1 resistor. The non-inverting terminal of the op-amp is grounded.

### Analysis

Case-1: When op-amp is ideal i.e. open-loop gain is infinite.

The analysis of the inverting amplifier circuit is shown in figure 2. Since the op-amp is ideal and negative feedback is present, the voltage of the inverting terminal (V) is equal to the voltage of the non-inverting terminal (V+ = 0), according to the virtual ground concept.

V= V+ = 0 Volt

The currents entering both terminals of the op-amp are zero since the op-amp is ideal.

(1) (2) Apply KCL at node P (3) From equations (1), (2) and (3), we have  The closed-loop voltage gain Av is given by From voltage gain Av, we can see that the output is 180° out of phase with the input.

Case-2: When op-amp has a finite open-loop gain, AOL (Practical case)

The analysis of the inverting amplifier circuit is shown in figure 3. Since the op-amp has a finite open-loop gain, Hence the voltage of the inverting terminal (V) is not equal to the voltage of the non-inverting terminal (V+ = 0) i.e.

V≠ V+

Assuming that the currents entering both terminals of the op-amp are zero.

(4) (5) Apply KCL at node P (6) From equations (4), (5) and (6), we have (7) As we know that,  (8) From equations (7) and (8), we have  The closed-loop voltage gain Av is given by  Therefore From voltage gain Av, we can see that the output is 180° out of phase with the input.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

error: Content is protected !!