01-07-2013, 04:26 PM
(29-06-2013, 06:50 PM)boiss Wrote: If this device was used in a complementary PP output stage then I would have thought that this could reach quite high values ie >20V
I've puzzled about this - in a normal complementary P-P stage the reverse Vbe doesn't reach more than one diode drop backwards - and is almost always less. When the bases are taken in such a direction to turn one transistor off, the other transistor turns on all the harder and takes the turned-off transistor's emitter with it.
As to can reverse Vbe do any harm? I have read that noise performance in small-signal devices (and on input stages of IC op-amps) can be degraded, but I have no experience of this. On the other hand, power switching stages are fairly often operated with Vbe in reverse breakdown to get the best possible turn-off speed. Current flow and duration are limited thus excessive energy dissipation in the wrong part of the device doesn't cause any thermal problems.
