Op-Amp as Comparator
Category: Operational Amplifier
Designer: RANA MUHAMMAD ADNAN KHALIL
Notes
This circuit is designed and simulated in Proteus 7.10. In this circuit you will learn how you can make comparator by using operational amplifier (op-amp). The working of this circuit is given below. 1. The op-amp used in this circuit is LM324. 2. To understand this circuit, you should have basics of op-amp or at least you should heard what is op-amp. 3. Op-amp has two inputs (one is inverting(-) and other is non-inverting(+)) and one output. 4. The inputs of op-amp has high impedance while output is low impedance. 5. A zener diode of 3.3V is used as a reference at non-inverting input. 6. The input signal is given at inverting input. 7. In this circuit, the op-amp is used in simple comparator configuration, therefore no feedback is used. This is also called open loop (without) circuit. 8. When the op-amp is used in open loop, its gain is infinity, thats why it is used as comparator. 9. The op-amp compare its inverting and non-inverting input, when the voltage signal at non-inverting pin is greater than inverting pin, the output of op-amp is high and when voltage signal at non-inverting pin is lower than inverting pin, the output of op-amp is low. Application 1. You can use this circuit where a voltage comparison is required. 2. This circuit is also used to detect water level and many other discrete detection's.