[time-nuts] Simulation

[Alan Melia]

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