From: Mike Monett
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Subject: Re: Amplifying stage with *negative* Voltage gain??
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Date: Fri, 06 Dec 2002 07:56:21 -0500
NNTP-Posting-Date: Fri, 06 Dec 2002 07:56:24 EST
Organization: Bell Sympatico
Paul Burridge wrote:
> On Thu, 05 Dec 2002 09:10:32 -0500, Mike Monett opined
> >Thanks for the reply. Tony raised a good point - what's the attenuation
> >of your scope probe?
> It's rated up to 60MHz, Mike. And switchable for X1/X10.
Do you get the same indicated voltage in either mode?
> >As far as a lower impedance driver, has you considered a complimentary
> >NPN/PNP pair with the bases and emitters tied together? You can use John
> >Larkin's trick of connecting a resistor between the bases and emitters to
> >reduce the crossover distortion. I tried this - it really works well.
> I don't doubt it, but right now I'm more concerned with trying to
> establish why this circuit as built doesn't conform to expectations.
> I'm determined to get to the bottom of it and with the assistance I've
> had from your good self and others here I'm optimistic that I may
> eventually prevail.
> "I was going to help him up, but then I thumped him."
> Michael Head's plea in mitigation to Weybridge Magistrates, Sept. 1975
Well, Paul, I've tried simulating your circuit with the emitter and collector
swapped, and with the collector open. In both cases, I get a lot more than 2V
So aside from a bad transistor, miswire, parasitic oscillation, bad probe,
scope out of calibration, probe out of calibration, poor bypassing, bad probe
ground, poor circuit ground, excessive wire length, mismarked component,
defective component, or a bad solder joint, I haven't got the foggiest clue
what could be causing the problem:)