Offset current changes caused by drift produce which effect in the circuit's output?

Offset current changes caused by drift produce which effect in the circuit's output?

• A. No effect
• B. Completely saturate the output
• C. Cause small errors in circuit output voltage
• D. Double the output voltage

Answer: (C)

Offset current drift introduces a small difference in the currents entering the two inputs of an op-amp. Those input currents flowing through the input and feedback resistances create a tiny input voltage error. With negative feedback, the amplifier will amplify that small input error, producing a correspondingly small error at the output. The size of this error depends on the resistance seen by the input currents and the amplifier’s closed-loop gain, so even though the circuit settles in its linear range, a slight, slowly varying output offset appears. It won’t normally be zero (because the currents aren’t perfectly balanced) and it won’t suddenly saturate the output unless the drift is large enough to drive the input error times the gain to a rail.

Offset current drift introduces a small difference in the currents entering the two inputs of an op-amp. Those input currents flowing through the input and feedback resistances create a tiny input voltage error. With negative feedback, the amplifier will amplify that small input error, producing a correspondingly small error at the output. The size of this error depends on the resistance seen by the input currents and the amplifier’s closed-loop gain, so even though the circuit settles in its linear range, a slight, slowly varying output offset appears. It won’t normally be zero (because the currents aren’t perfectly balanced) and it won’t suddenly saturate the output unless the drift is large enough to drive the input error times the gain to a rail.