[Amps] Delicate Transistors....?

[gw4dgu at blaenffos.org]

"Dr. William J. Schmidt, II" wrote:

>'whereas transistor amps would go south almost immediately'

Hmmmmm... That's not really the case. There seems to be an idea amongst many
amateur amplifier builders that solid-state devices are somehow unreliable
and delicate. That's really the opposite of the truth. If transistor (or
nowadays FET) amplifiers are built with the same degree of care,
understanding and attention to detail as tube amplifiers, they should be
very much more reliable than tubes. An MTBF of 100000hours would be thought
on the low side for a power FET, whereas there are few tubes, which will
pass 10000hours without some loss of performance, even when operated
conservatively. Of course amplifiers combined using hybrids without the
isolating termination are likely to fail - after a short period of
spectacular cross-coupled oscillation - whether they use tube or ss devices!

The myth that power transistors will fail if they see a poor return-loss for
even a microsecond comes from the early days of BJT power device development
when devices had to pushed to their limits to get useful power. Except in a
few rather special applications that hasn't been true for 20years. RF Power
device technology is now mature, and costs have fallen substantially.
Returning to active amateur radio after around 15years QRT, I have no
intention of ever building valve amplifiers again! (Although I do keep the
ability to design them on my professional CV (resume)...!)

73

Chris
GW4DGU - EME without a tube in sight....