Gain stability of feedback amplifiers

The degree of gain stability which feedback confers upon an amplifier is a function of both the magnitude and the phase angle of the loop gain. By proper choice of this phase angle, either the magnitude or the phase angle of the gain with feedback may be made independent, to a first order, of changes in the active elements, and over a narrow frequency range an amplifier can be made to be as stable as the passive components in the feedback network. The general theory is developed, and some results obtained with an experimental amplifier are described.