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From: John Woodgate
Subject: Re: Choosing Feedback Resistors for Op Amp
Date: Tue, 1 Oct 2002 19:04:26 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Tue, 1 Oct 2002 19:12:52 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Julian wrote (in ) about
'Choosing Feedback Resistors for Op Amp', on :
> So resistors must be chosen to match the input and output
>impedances of the op-amp to the rest of the circuit.
That would be *extremely* misleading if 'matching' were understood in
its traditional sense (matching for maximum power transfer).
Regardless of all the complications, the feedback resistor (output to
inverting input) is almost always between 1 kohm and 1 Mohm, and the
other gain-defining resistor (inverting input to ground or input
terminal) resistor is normally between 100 ohm and 10 k ohm. If the
required gain is less than 10, make both resistors between 1 kohm and 10
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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