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From: "Phil Allison"
References: <firstname.lastname@example.org> <email@example.com>
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 22:46:00 +1100
NNTP-Posting-Date: Wed, 20 Nov 2002 22:35:35 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"Paul Burridge" wrote in message
> On 19 Nov 2002 15:35:20 -0800, firstname.lastname@example.org (N. Thornton) opined
> >You say you have biasing / temp compensating there, yet its meant to
> >be class B: how is that so? For real class B you don't need to apply
> >any bias chain, so there should be no need for temp compensation.
> You certainly have to provide *drive current* to the bases and this is
> the chain through which it's provided. And with all due respect, your
> claim that class B doesn't require temp.compensation is at odds with
> everything I've thus far read on the subject in a number of books.
** Some temp compensation is needed to keep the OP stage in pure class
B *despite* large chip temp changes and hence Vbe changes.
The Crown DC300 A is a good example with 350 mV on the OP device
base-emitter junctions at idle and much less when really hot.
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