ABSOLUTE_VALUES

Published:2009/7/15 2:04:00 Author:Jessie | From:SeekIC

Positive output signal level is proportional to absolute value of input signal level, regardless of input polarity. Circuit combines simplicity with high input impedance, low output impedance, and greater than unity gain. Opamps A1 and A2 should have good CMRR and low offset and drift. D1 and D2 can be 1N914 For gain of 2.5, R1 and R3 are 1000 ohms, R2 is 2500, nd R4 is 2333 For unity gain, R4 is infinity and can be omitted R2 and R3 areequalue precision resistors Value of R1 is not critical at any gain．-R. Hofheimer, A Simple Absolute-Value Amplifier, EDN Magazine. June20, 1974, p 78 and 80.



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