[Amps] Power Transistor Question -- 2SC5125

[Peter Chadwick]

Manfred said:
>First, that you allow the junction to heat up to its 
absolute maximum momentary temperature, 200 degrees Celsius. Running the 
transistor that hot will allow it to last only for a very short time, 
maybe just hours! You should run it at no more than 150 degrees to 
obtain a good (almost eternal) lifespan.<

To give some idea of how the life shortens......the company I work for used to make transistor arrays. We sold some to go into oil well drills, guaranteed to have a minimum life of 30 minutes (!) at a chip temperature of 260deg C. And, naturally, we charged for them........the same chip at 125 deg C junction temperature would exceed 1 million hours on the standard failure rate extrapolations from burn in.
Having said all that, in my ham gear, I've had more semiconductor failures in the last 20 years than tube failures. Possibly part of this is that I have considerably more semiconductors than tubes, but in terms of overall equipment reliability, it's a sobering thought.....
73
Peter G3RZP