How comparator circuit works? Simple concepts in the study of comparator using opamp

Comparator is a circuit with two input terminals i.e. inverting and non-inverting. A standard voltage known as reference voltage Vref is connected to either inverting or non inverting terminal.

When it is connected to inverting terminal the input voltage Vin to compare is connected to non-inverting terminal or vice versa.

When the Vref = 0 and it is connected to inverting terminal, the circuit is called as INVERTING ZERO REFERENCE COMPARATOR. When it is connected to non-inverting terminal, the circuit is called as NON-INVERTING ZERO REFERENCE COMPARATOR.

When the Vref > 0 and it is connected to inverting terminal, the circuit is called as INVERTING NON-ZERO REFERENCE COMPARATOR. When it is connected to non-inverting terminal, the circuit is called as NON-INVERTING NON-ZERO REFERENCE COMPARATOR.

Whatever may be the input condition, the output of the comparator can have only three possible values i.e. output voltage Vo = +Vsat (Fully saturated positive voltage) or output voltage will be as such that it will beVo = –Vsat (Fully saturated negative voltage).

Now consider inverting zero reference comparator. For this the value ofVref = 0. The input voltage Vi is connected to non-inverting terminal. There are three possible conditions in this circuit, as follows –

When Vi > Vref, Vo = –Vsat

When Vi < Vref, Vo = +Vsat

When Vi = Vref, Vo = 0

Now consider inverting non-zero reference comparator. Let Vref = 3V. The input voltage Vi is connected to inverting terminal. There are three possible conditions in this circuit, as follows –

When Vi > Vref = 3V, Vo = –Vsat

When Vi < Vref = 3V, Vo = +Vsat

When Vi = Vref = 3V, Vo = 0

The above conditions occur because you are connecting higher i.e. positive voltage, which is greater than zero to inverting terminal. And the inverting terminal has the property to revert the polarity or sign of the voltage connected to it. So to understand the working of comparator just remember the property of inverting and non-inverting terminals of the operational amplifier.

Note: All these conditions will be exactly reversed and applicable to other circuit i.e. to the circuit of non-inverting zero reference comparator or the non-inverting non-zero reference comparator.