# Op-Amp comparator – working, waveforms and analysis

## Op-Amp Comparator:

In this section we are going to learn a basic op-amp application as a comparator. Comparator is a circuit used for comparing two voltages (either DC or both AC or one DC & one AC) and indicating the relationship between those voltages.

Generally comparators are used to compare either:

a)      Two changing voltages to each other, example: two different sinusoidal waveforms.

b)      A changing voltage to a set DC reference voltage.

The circuit diagram of op-amp comparator is sown below. There is no feedback path present in the circuit. To understand the working of op-amp comparator let us consider a sinusoidal input voltage is applied to the non-inverting terminal where as a fixed DC voltage (V reference) is applied to the inverting terminal.

### Circuit diagram:

In this example we are going to compare sinusoidal voltage with fixed dc voltage using op-amp comparator. The working of this comparator is explained as follows.

### Working:

As long as the input voltage is below the reference voltage (which is connected to the non-inverting terminal) , the comparator output is approximately “-Vmax” volts. When input voltage equals to reference voltage or exceeds, the output voltage of the comparator becomes “+Vmax” volts. Thus op-amp comparator shows the relationship between the magnitudes of two voltages applied to its input. Following figure shows the polarity (or magnitude) relationship between two voltages.