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From: "Phil Allison"
Subject: Re: Class B amplifiers: what are the large low-value resistors for?
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Wed, 20 Nov 2002 08:21:45 +1100
NNTP-Posting-Date: Wed, 20 Nov 2002 08:11:42 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"Paul Burridge" wrote in message
> On Tue, 19 Nov 2002 23:47:40 +1100, "Phil Allison"
> opined thusly:
> > ** Three bias diodes sounds like a quasi complementary design - ie
> >outputs are NPN and the drivers are NPN and PNP - is that the case ?
> You mean as in a Sziklai connection? Nope. The output transistors are
> definitely PNP and NPN. and they are single devices and not
> 'sub-driven' in any kind of Darlington arrangement. The driving stage
> just uses one NPN whose collector feeds both bases of the output pair.
> > ** This is sounding weird - with even one diode shorted there is no
> Correct. At least in theory. Sadly not in this experimental circuit.
** You have made a dumb mistake in the wiring.
> > ** The schematic has to be revealed and the type numbers too.
> Its actually a *very* simple final stage indeed. I personally can't
> see where all this forward bias is coming from.
** There should be no more than two bias diodes then and with no
drivers it is not going to work very well.
Maybe the outputs SHOULD be darlingtons.
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