Switching Transients of Transistors with Speed-up Capacitors

ABSTRACT

Generalized expressions for switching times of a transistor employing speed-up capacitor have been derived from the charge-control equivalent circuit of the device and the effect of the duration of the ‘On’ pulse on switching times has been studied.

During the turn-off transient of a typical switching circuit with a speed-up capacitor, the transistor turns off first but becomes conducting again for a while before finally turning off. This phenomenon known as ‘wiggle effect’ is undesirable in practical switching circuits. The probable cause for this phenomenon has been investigated and the effectiveness of a typical compensation circuit to minimize the wiggle effect has been studied for various types of devices like the alloy, MADT and epitaxial planar transistors.