ANALOG_PREAMP

Published:2009/7/10 3:28:00 Author:May | From:SeekIC

Combination of 5-kHz FET-chopper amplifier Q1-Q2 with transformer isolation of signal and system grounds gives low-cost analog instrumentation amplifier that will process millivolt DC signals while rejecting hundreds of volts of common-mode DC. Signal accuracy is 0.1% for inputs between 50 and 500mV. Input impedance is 4 megohms, drift is only 0.2μV/℃, and DC common-mode rejection rate is better than 120 dB. Low-impedance output of followers Q3－Q4-Q5 is sent through T1 to synchronousFET demodulator Q6-Q7,R7 adjusts system scaling.C.A.Walton,High-CMR,Low-Cost DC Instrumentation Preamp,EDN Magazine,Jan 15,1971,p 47－48.



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