Troubleshooting Techniques

1. Verify the op-amp dc output offset voltage. If the op-amp uses a dual supply, the offset voltage  few mill volts. • Faults in the Noninverting Amplifier • Faults in the Inverting Amplifier • Open Feedback Resistor(Rf) • If Rf open, op-amp operate at very high open-loop gain. • Result: Output signal clipped • Open Feedback Resistor (Rf) • If Rf open, the signal will still amplified by the high open-loop gain. • Result: Output signal clipped • Open Input Resistor(Ri) • If Ri open (i.e. infinite), the closed-loop gain become 1 • Results: Output signal = Input signal • (Amplifier acts as voltage-follower) • Open Input Resistor(Ri) • If Ri open, no input signal to op-amp • Result: No output signal Rf Open Ri No Output Signal Vin Troubleshooting Op-Amps Troubleshooting Techniques • Make sure power supply voltages are normal and it is good idea to measure voltages (and signals) directly on the IC Pins • A simple test can be used to identify that an op-amp is at least working. Figure below shown how the test is done. Simply short the input temporarily to V+ and then to V-, the output voltage should swing from near V- to near V+. If it fails, you can be fairly certain the IC is bad.