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From: Tony Williams
Subject: Re: Amplifying stage with *negative* Voltage gain??
Date: Tue, 10 Dec 2002 22:37:07 +0000 (GMT)
References: <firstname.lastname@example.org> <3DEF1DC0.5EDD@Spam.Bots> <email@example.com> <3DEF5BEA.2614@Spam.Bots> <3DF0A422.46EE@Spam.Bots> <firstname.lastname@example.org> <3DF263CE.3868@Spam.Bots> <email@example.com> <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
NNTP-Posting-Date: Tue, 10 Dec 2002 22:38:58 +0000 (UTC)
User-Agent: Pluto/1.14i (RISC-OS/3.60)
In article <email@example.com>,
Paul Burridge wrote:
> opined thusly:
> > Lift the emitter and the emitter resistor up off the
> > stripboard, join them together in mid-air. Connect
> > nothing else there. There is clearly then no load of
> > any sort on the joint. Look at it directly with the
> > scope only.... X1 and X10. See what you get.
> I've done what you suggest. On x10., the readings are now 2v p-p for
> sig in; 2.4v p-p for sig out.
> With x1., the readings are 8v p-p for Vin and 2.4v p-p for Vout.
> Isn't this where we came in?
Just to turn things on their head.... that 2.4v p-p
on the output now looks nicely consistent, with the
8v p-p measurement maybe looking suss. Perhaps the
input signal source is somehow being disturbed by
the X1 scope probe.
Clip say a 1k resistor in series with the scope probe
and have a look again. All voltages will be reduced,
but the 1k will provide some local resistive isolation
of the scope probe.
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