Using this circuit diagram you can make an electronic tester for operational amplifiers. This operational amplifier tester allows a quick functional verification of operational amplifiers. For test this amplifier is connected as a simple square wave generator.
When S1 is pressed, the noninverting input of operational amplifier reaches a reference voltage which is the result of the output voltage divider R2/R3 voltage. Capacitor C1 is charged via R1 until the voltage at the inverting input is equal to the reference voltage. Since the operational amplifier working as a comparator, the output switch and reference voltage gets opposite polarity. Capacitor C1 charge properly again until the voltage reaches the reference voltage.
When operational amplifier output potential test is positive, T1 conducts and D1 LED lights, and if the operational amplifier is switched and output to a low potential, T2 conducts and D2 LED lights.
Transistor T1 may be BC107, BC547 transistor type and T2 may be a BC177 or BC557 type.