Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2.fluke 9/24/84; site vax3.fluke.UUCP
Path: utzoo!decvax!ittatc!dcdwest!sdcsvax!sdcrdcf!hplabs!tektronix!uw-beaver!fluke!szepesi
From: szepesi@fluke.UUCP (Les Szepesi)
Newsgroups: net.analog
Subject: Suggestions on measuring ac CMRR
Message-ID: <1704@vax3.fluke.UUCP>
Date: Thu, 8-May-86 13:42:16 EDT
Article-I.D.: vax3.1704
Posted: Thu May  8 13:42:16 1986
Date-Received: Mon, 12-May-86 00:05:18 EDT
Distribution: na
Organization: John Fluke Mfg. Co., Inc., Everett, WA
Lines: 20

I need to measure the ac common mode error of a wideband amplifier as a function
of both amplitude and frequency. I have used servo-loop test circuits (similar
to the one described in the Analog Devices application note "How to Test
Basic Operational Amplifier Parameters") to measure CME at dc. However, the
integrator used in this method makes it impractical for ac measurements.

What I am looking for is a way to do this without having to have highly matched
ac attenuators which would be required for a measurement in a differental
configuration. (.1% mismatch ~= 60dB >> expected CMRR)

I presume there is a convenient way to do this, since many op amp spec sheets
have plots of CMRR vs. frequency.

Thanks in advance.
-- 
Les Szepesi		decvax\
John Fluke Mfg Co.	ihnp4  >!uw-beaver\
PO Box C9090    MS 274G		   allegra >!fluke!szepesi
Everett, WA 98206 USA	ucbvax >!lbl-csam /
(206) 356-6362		hplabs/