Amplification Circuit:

The amplification circuit, that could be a magnetic amplifier or transistor amplifier, takes the signal from the comparison circuit and amplifies the milliamp input to an amp output, that is then sent to the signal output, or circuit, field.

Signal Output Circuit

The signal output circuit, that controls field excitation of the AC generator, rise or decreases field excitation to either increased or lower the AC output voltage.

Feedback Circuit

The feedback circuit will takes a few of the output of the signal output circuit and feeds it back to the amplification circuit. It does this to avoid undershooting or overshooting of the desired voltage through slowing down the circuit response.