Deane Jensen
Jensen Transformers

For the scope of this text, stable operation of a feedback amplifier describes a condition which exhibits no oscillations, no overshoot, and no peak in the closed loop response. Of course, equalizer and filter circuits can have overshoot and peaks without instability; these will be discussed after the general case of the wideband "flat" gain block. Stable operation also results in relative freedom from RF sensitivity and the type of clicks and pops which are actually bursts of oscillation triggered by an external transient noise source. Good stability and low overshoot will result only if the feedback circuit response determines a reasonable amount of feedback at all frequencies of open loop gain. Often that means up to 10 MHz. Low overshoot and ringing means freedom from transient distortion caused by oscillations trailing each steep slope of the waveform.