6 Mar
2008
6 Mar
'08
3:13 a.m.
Roger Holmes wrote:
Tony Duell wrote:
Roger Holmes wrote:
Not so useful
with peripherals though, I find a storage scope is
invaluable for them, the more traces the better, so I suppose a logic
analyser would be useful, but does one exists for MINUS 6.3 volt
logic? I always presumed they were only invented after silicon
replaced germanium and so only work with positive logic voltages.> >
I fail to see
what silicon .vs. germanium has to d owith the
polarity of
the logic cignals. In general PNP transistors, and for that matter
PMOS
fets, imply -ve logic levels, and plenty of machines were built using
those components. Also ECL chips have -ve logic levels (around -2V)
wrt
ground.
I bow to your greater knowledge. I was employed as a
programmer and
picked up hardware later.
Most Ge transistor equipment (pre-mid-60's) was PNP/-V, most post-mid-60's
was Si/(NPN if bipolar)/+V, as per the supposition of your (Roger's)
original question.
Historically, or in terms of the prevalence of according systems, there
is a correlation between the material and the polarity, although it's
not a technically imperative correlation (there are exceptions).
I'm not sure of the cause of the correlation, a guess would be that
manufacturing issues lent a preference to Ge-PNP and Si-NPN.