Op-amp (Operational Amplifier) is very important component in Electronics, and used in many Electronics circuits to serve different purposes. We have used different Op-amps in many circuits and developed a separated section for Op-amp Circuits.
Op-amp basically has Voltage Comparator inside, which has two inputs, one is inverting input and second is non-inverting input. When voltage at non-inverting input (+) is higher than the voltage at inverting input (-), then the output of comparator is High. And if the voltage of inverting input (-) is Higher than non-inverting end (+), then output is LOW. Op-amps have large gain and usually used as Voltage Amplifier. Some Op-amps have more than one comparator inside (op-amp LM358 has two, LM324 has four) and some have just one comparator like LM741.
Op-amp Tester Circuit:
Sometimes we start with a working circuit and then after some time we find that circuit is not working. After some testing we find that one of the components has been burned. Now how to test the components for fault? We have previously built a Transistor Tester Circuit to test transistor and now we are building Simple Op-amp Tester Circuit to test the LM741 IC. IC LM741 is advanced and commonly used Op-amp as voltage amplifier. Pin diagram of LM741 is given below:
Circuit Diagram and Working:
Circuit is very simple and we have kept is simple with few components, which can be easily built on breadboard or on PCB.
We just need to place the op-amp LM741 on right place and if the Op-amp is in good condition then LED will flash or Blinks, and if Op-amp is faulty then either LED will remain ON or OFF continuously.
Working of the circuit is simple, basically this circuit generates a Square wave at the output if op-amp is in working condition, resulting a Blinking LED. When we ON the circuit with op-amp is in place, initially voltage at non-inverting input (+) is higher than the voltage at inverting input (-) and output of op-amp LM741 (PIN 6) is High. So capacitor C1 starts charging through the resistor R6, when C1 charging exceeds the voltage at inverting terminal (PIN 2), then output becomes low. And when the output goes Low, capacitor C1 starts discharging and again voltage at inverting terminal of comparator becomes lower than non-inverting terminal and output goes High. This process repeats continuously and produces Square Wave at the output, which causes LED to Blink.
So if the Op-amp is in working condition, then LED will blink continuously at regular interval and if op-amp is faulty then LED will either stays ON or OFF.
This process of charging and discharging of capacitor is much similar to 555 timer IC in Astable mode, which also produces square wave at the output.