Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
References: <email@example.com> <firstname.lastname@example.org>
Subject: Re: Class B amplifiers: what are the large low-value resistors for?
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X-Inktomi-Trace: public1-pete2-5-cust19.pete.broadband.ntl.com 1037792831 26962 18.104.22.168 (20 Nov 2002 11:47:11 GMT)
Date: Wed, 20 Nov 2002 11:47:07 -0000
NNTP-Posting-Date: Wed, 20 Nov 2002 11:47:11 GMT
Paul Burridge wrote:
> On 19 Nov 2002 15:35:20 -0800, email@example.com (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.
*Pure* class B dose not require temperature compensation. Temperature
compensation is to compensate the *bias* current. If there is no bias
current, there is nothing to compensate. The reason for this
misunderstanding could be that is usually to say class B as shorthand,
when in fact one rarely uses class B, it is always class AB, i.e. there
is at least some standing current.
The only commercial audio amplifier I am aware of that used a pure class
B output was the Quad current dumper.
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