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From: Paul Burridge
Subject: Re: Amplifying stage with *negative* Voltage gain??
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Date: Tue, 10 Dec 2002 14:06:30 +0000
NNTP-Posting-Date: Tue, 10 Dec 2002 15:34:51 GMT
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On Tue, 10 Dec 2002 13:52:56 +0000 (GMT), Tony Williams
> Your reported "flattened bottom half" is suggestive
> of a capacitive load on the emitter.... either the
> 1nF and a load outboard of it, or a direct capacitor
> on the emitter.
Just to clarify, the *really* flattened out waveform occurred when I
did the c/e pin swap that someone suggested. Now I've gone back to
what I believe beyond reasonable doubt is the correct pin-out, the
waveform is much less distorted. But it still ain't a pure sine wave
as the trace is kinda tear-shaped; pointy on the positive peaks but
noticeably bulbous on the negative ones. But it's not actually
bottoming out as it was when the pins were transposed.
Actually, to be fair, a good deal of this distortion is originating
from the osc. stage. Probably not enough capacitive loading giving
A rather ropey looking signal to start with.
> 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?
"I was going to help him up, but then I thumped him."
Michael Head's plea in mitigation to Weybridge Magistrates, Sept. 1975
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