The provision in an amplifier of negative feedback of such amplitude and phase that it counteracts any inherent positive feedback. If the positive feedback is not neutralized, unwanted oscillations may occur.

Unwanted positive feedback in an amplifier can arise from the Miller effect and is counteracted by neutralization: a circuit is used to provide a 180° phase shift in the voltage fed back to the input (base) circuit. Parasitic oscillations produced during push-pull operation can be counteracted by cross neutralization, in which a portion of the output voltage of each device is fed back by means of a neutralizing capacitor to the input (base) circuit of the other device.

The voltage fed back to the input is termed the neutralizing voltage. The degree of neutralization in an amplifier may be observed using an indicating device termed a neutralizing indicator.