1.1.1) Saturating Precision Half-Wave Rectifier Circuit Operation
When input signal is positive, the diode is forward biased and the output voltage follows the input.
Recall that negative feedback causes the voltage at the inverting input terminal to follow that at the noninverting terminal.
Since the output of the circuit and the inverting terminal are common, the output follows the input within microvolts.
The diode forward voltage drop is not involved.
While the input voltage is in its negative half-cycle the op-amp output is negative and the diode is reversed biased.
Consequently, the feedback path is interrupted, the inverting input terminal remains at ground level (because RL is grounded), and the op-amp output is saturated in a negative direcrion.
The negative half-cycle of the input does not pass to the output; it is clipped off.
If the diode polarity is reversed in Fig.7-1(a), the negative half-cycle of the input waveform will be passed to the output and the positive half-cycle will be clipped off.