A destructive instability in selective high-power amplifiers with bipolar transistors

An oscillation mode is described which, under certain circumstances, can be excited in selective high-power amplifiers with bipolar transistors. This instability can arise after a single saturation of the transistor and does not depend on feedback or parasitic elements. It is caused by the storage time of the transistor after a saturation. Out of the oscillation mechanism it is shown that transistor voltages and currents during this oscillation mode can be manifold the values of the normal operation. On this account, usually one or a few oscillations of this mode destroy the output transistor, either by voltage of current overload. A computation method is shown with stability charts which describe stability conditions of a given amplifier, depending on the values of the elements of the peripheral circuitry.