Comparator
A comparator is a circuit that accepts two voltages, V1 and V2 and outputs zero volts if V1 > V2 or outputs a positive voltage level if V2 > V1. Comparators can be built from operational amplifiers.
In laments term, a comparator is the simplest circuit that moves signals between the analog and digital worlds…
Simply put, a comparator compares two analog signals and produces a one bit digital signal. This is the symbol for a comparator

* The comparator output satisfies the following rules: * When V+ is larger than V- the output bit is 1. * When V+ is smaller than V- the output bit is 0

A prime example of a simple comparator circuit can be found within a programmable thermostat. With two separate inputs, three outcomes are achievable at any given time. When the base input becomes lower than the variable, a signal will be sent to the thermostat to activate the cooling feature, and that circuitry will allow that function to occur until both the base and variable are once again equal. At that point, the air conditioner would shut off until further instructions were provided.
If the variable electrical node provided less electrical power than the constant, a signal would be generated to inform the thermostat to activate the heating element. It would remain on until the variables changed once again. Each of these functions are pre-programmed to react differently as the values change, and the comparator circuit design interprets them by analyzing the variable