Op Amp pinouts was Re: [sdiy] more LM3900 stuff

[harrybissell]

"JH." wrote:

> A former colleague at Siemens (now retired) claimed that it was him who
> demanded that the manufacturer (Fairchild? - not sure) changed the design
> to get rid of phase reversal, in order to qualify that chip for use in
> nuclear power
> plants.

HAH. Good one.  I had a design (not mine) that used the OP-07... which
they
later substituted the OP-77 (improved, yeah right).  Don't know WHY they
switched because the OP-07 still lives. Maybe a boat was involved in the 
purchase decision.

Now this was in a servo HEATER loop... so when the OP-77 did the 'phase
reversal'
thing (OP-07 doesn't)... the heater sensed it was too hot, so it turned
the power
UP. (change of sign can be very serious in a closed loop :^).  This if
unnoticed
would trash the $150 heater wire (Platinum) and maybe take the Vicor
tube ($700)
and the sensor ($1,000).

I had never seen 'phase reversal' then. It was an expensive lesson. We
noticed by
dumb luck that the OP-07 never had a problem. Only years later did I
recognise
the root cause :^)

I understand the nuclear option. China Syndrome, anyone ???

H^) harry