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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: Final final 1kHz oscillator
Date: Wed, 20 Nov 2024 17:36:18 -0000 (UTC)
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john larkin <JL@gct.com> wrote:
> On Sun, 17 Nov 2024 02:01:25 +0000, JM
> <sunaecoNoChoppedPork@gmail.com> wrote:
> 
>> On Thu, 14 Nov 2024 11:14:28 -0500, "Edward Rawde"
>> <invalid@invalid.invalid> wrote:
>> 
><snnnniiiiiipppp>

>> Because of common mode (non)linearity.  In most op-amps (especially
>> older designs) the distortion generated by the common mode signal is
>> typically one to two orders of magnitude larger than the transfer
>> distortion.  If it is not clear from the data sheet, it is best to
>> measure the CM performance or just assume that it's 40dB worse than
>> the specified figure.
> 
> To quote Jim Williams, "always invert."
> 
“Except when you can’t.”

> Just the ESD diodes are a distortion hazard. I've seen people
> bootstrap the power supplies to improve CMRR.
> 
>
Pease has an article somewhere about how to measure CMR and PSR
correctly—as he says, most of the obvious methods actually measure
open-loop gain. 

Cheers 

Phil Hobbs 



-- 
Dr Philip C D Hobbs  Principal Consultant  ElectroOptical Innovations LLC /
Hobbs ElectroOptics  Optics, Electro-optics, Photonics, Analog Electronics