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Yes used to be a well known "phantom supply"
effect. Another effect which I dont think effects CMOS because I dont think
there are any layers that used to be called "substrates". In some MOS devices
like the AMD7910 (PMOS ??) used in a lot of packet modems and also the Texas
Bell Modem chip,.......if you left audio going into the modem chip from the
radio with the TNC power off the internal substrate would charge up though
the isolation diodes until the input was biassed completely to cut off the input
signal. It was often refered to as the "deaf modem" effect. It could be
recovered by heating the chip to about 120deg C and leaving it unpowered for
several days to allow the excess charge to leak away as the reverse diode
leakage was increased with temperature.
A variant of this signal-powering was used by
several ADCs (Pico Technology, and I think Andy used it on a PIC) of
toggling the RS-232 modem control lines and rectifying the signal to supply
power in the days before powered USB.
The only bad effect I came across with CMOS was
where the ground rail (or input) was taken more than 1v above the Vdd in a short
pulse. This caused an internal 4-layer structure mimicking a thyristor to switch
on shorting the supply rail to ground. This usually produced a crater effect
over the chip in plastic devices, or if the supply was beefy enought blowing the
encapsulation to pieces.
Alan
G3NYK
----- Original Message -----
Sent: Wednesday, March 02, 2016 12:22
PM
Subject: Re: LF: A divider with no power
supply
Yes, I had that once.
Surreal, isn't it ;-)
'jnt
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