Re: Operational Amplifier Design

From: Ken Smith (kensmith_at_green.rahul.net)
Date: 11/08/04 

Date: Mon, 8 Nov 2004 21:48:46 +0000 (UTC)

In article <kuuuo055ldqf0oam7oit783ljcas7t85os@4ax.com>,
Paul Burridge <pb@notthisbit.osiris1.co.uk> wrote:
>On 7 Nov 2004 18:26:07 -0800, Winfield Hill
><whill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:
>
>>Ken Smith wrote...
>>>
>>> Winfield Hill
>>>> The LM324 output stage is severely in need of improvement...
>>>
>>> If the OP is just trying to get a starting point, operation down
>>> to the negative rail can be set aside. Yes the output stage sucks
>>> but it is simple.
>>
>> Simple, but pedagogically best as an example of how not to do it.
>
>It can't be *that* bad. In that poll of "classic chips" we had last
>year, the 324 was one of the most popular, ISTR.

The output section has about 3 diodes worth of crossover distortion and
the compensation does not enclose that distortion so at high frequencies,
it appears in the output. It also makes the output impedance rise quite a
bit for increasing frequencies and vary a lot with load current. This can
lead to trouble when you use them to drive a transistor buffer. 

-- 
--
kensmith@rahul.net   forging knowledge

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