Op-Amp as Comparator
Category: Operational Amplifier
Designer: RANA MUHAMMAD ADNAN KHALIL
Video — how it works
Watch the Op-Amp as Comparator explainer on YouTube
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.