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From: Mike Monett
X-Mailer: Mozilla 2.02 (Win16; I)
Subject: Re: Amplifying stage with *negative* Voltage gain??
References: <firstname.lastname@example.org> <3DEF1DC0.5EDD@Spam.Bots> <3DEF5E58.3DF5@Spam.Bots> <email@example.com> <3DF09E75.7BDF@Spam.Bots>
Date: Fri, 06 Dec 2002 09:52:30 -0500
NNTP-Posting-Date: Fri, 06 Dec 2002 09:52:32 EST
Organization: Bell Sympatico
- René - wrote:
> On Fri, 06 Dec 2002 07:56:21 -0500, Mike Monett wrote:
> >Paul Burridge wrote:
> >> On Thu, 05 Dec 2002 09:10:32 -0500, Mike Monett opined
> >> thusly:
> >> >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.
> >> --
> Apart from all the above / earlier, I am still curious what the
> results are for a smaller Re. Hfe usually varies with average Ice,
> and for a HF amp I would hesitate to use such a large value resistor.
> - René
Sorry for replying by email. I hit the wrong button on my browser.
Of course you are right. The first thing is to get the circuit
behaving properly to give Paul confidence it will work. Then
If the awful truth be known, a 2N2222 will be unable to drive 8V p-p
into a capacitively-coupled 50 ohm load. The power dissipation will
exceed the capability of the device. One suggestion is to use John
Larkin's trick as mentioned above. If the residual distortion is too
high, a simple Tchebycheff low-pass filter can eliminate the
harmonics. But it takes power to drive this, so a better driver is
The next problem will be to do it at 100MHz:)
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