[time-nuts] Simulation

J. Forster jfor at quik.com
Sun Aug 15 22:17:04 UTC 2010


It depends on whether the leakage continues to rise or stabilizes after a
"burn in" period.

-John

============


> Hi Bob yes that was a point raised by Prof Nat Sokal after I published
> some
> data, or rather he pointed out it happened in RF amps. I guess if you take
> an used PA transistor out of service and measure it you might find the
> base
> emitter junction very leaky, but does  few mA of leakage matter so much in
> a
> low impedance high drive power circuit.
> Reliability asks "does it do the job it was designed for" not "is it as
> good
> as new now"
>
> Alan
> G3NYK
> ----- Original Message -----
> From: "Bob Camp" <lists at rtty.us>
> To: "Discussion of precise time and frequency measurement"
> <time-nuts at febo.com>
> Sent: Sunday, August 15, 2010 1:33 AM
> Subject: Re: [time-nuts] Simulation
>
>
>> Hi
>>
>> Simulation might or might not have helped.
>>
>> 1) Was Vbe breakdown even included in the Spice model
>> 2) If so did it ring bells (rare) or did it just clip without error (
> common )
>> 3) Would the same designer who didn't understand it in the first place
> have seen it clipping at -5 and concluded "looks to be in spec at -5"
>> 4) Would any of it be reviewed in light of the new transistor or was the
> guy on another project by then
>>
>> My favorite in the absolute max Vbe category is the typical class C RF
> amp. Look at the spec, check a few thousand working boards. Scratch head
> and
> move on. Lots of reverse bias on the base and they run forever.
>>
>>  Bob
>
>
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