Assume that the op-amp shown below is ideal. Find vo(t) for all t.
Solution
I. The output attempts to do whatever is necessary to make the voltage difference
between the inputs zero. II. The inputs draw no current. Comments on 1: The voltage gain
of a real op-amp is so high that a fraction of a millivolt input will swing the output over its full
range. Practically, that amounts to rule 1. Comments on 2: The input current is so low (0.08
microamps for the 741, picoamps for an FET-input op-amp) that rule 2 is practically correct
Solution
I. The output attempts to do whatever is necessary to make the voltage difference
between the inputs zero. II. The inputs draw no current. Comments on 1: The voltage gain
of a real op-amp is so high that a fraction of a millivolt input will swing the output over its full
range. Practically, that amounts to rule 1. Comments on 2: The input current is so low (0.08
microamps for the 741, picoamps for an FET-input op-amp) that rule 2 is practically correct
