Comparator

Comparator

• A comparator is a device that compare a measurable quantity with a reference or standard such as two voltages or currents. They are commonly used in devices that measure and digitize analog signals. Comparators

Non-Inverting Comparator

• A comparator compares a signal voltage applied at the input of an op-amp with a known reference voltage Vref given at the other input.
• It is an open-loop operation, i.e., there is no feedback path in the case of a comparator. Non-Inverting Comparator

Working of Non-Inverting Comparator

• A fixed reference voltage Vref of 1 V is applied to the negative terminal and time varying signal voltage Vin is applied to the positive terminal.
• When Vin is less than Vref the output becomes V0 at –Vsat [Vin < Vref => V0 (-Vsat)].
• When Vin is greater than Vref, the (+) input becomes positive, the V0 goes to +Vsat. [Vin > Vref => V0 (+Vsat)].
• Thus the V0 changes from one saturation level to another.
• The diodes D1 and D2 protect the op-amp from damage due to the excessive input voltage Vin. Because of these diodes, the difference input voltage Vid of the op-amp diodes are called clamp diodes.
• The resistance R in series with Vin is used to limit the current through D1 and D2. To reduce offset problems, a resistance Rcomp = R is connected between the (-ve) input and Vref. Working of Non Inverting Comparator

Inverting Comparator

• This comparator is called as inverting comparator because the input voltage, which has to be compared is applied to the inverting terminal of op-amp. Inverting Comparator

Working of Inverting Comparator

• In this circuit Vref is obtained by using a 10K potentiometer that forms a voltage divider with DC supply volt +Vcc and -1 and the wiper connected to the input.
• As the wiper is moved towards +Vcc, Vref becomes more positive.
• Thus a Vref of a desired amplitude and polarity can be got by simply adjusting the 10k potentiometer. Working of Inverting Comparator