LEVEL_INDICATOR

Published:2009/7/14 22:10:00 Author:Jessie | From:SeekIC

Visual indication of voltage level is achieved with two TIL203 LEDs, three resistors, and any opamp that can provide 15-mA output current. If input voltage momentarily or permanently exceeds most positive reference level, LED1 is switched on. If voltage falls below negative or least positive reference level, LED1 goes off and LED2 comes on. Article gives design equations for determining values of R1 and R2. For levels of +2 V to turn LED1 on and -1.2 V to turn LED2 on, both R1 and R2 are 10K.-E. J. Richter, Op Amp Makes Visual Level Indicator, EDN Magazine, May 5, 1974, p 73.



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