GAIN_PROGRAMMABLE

Published:2009/7/14 4:41:00 Author:May | From:SeekIC

Gain of non-inverting opamp can be programmed with standard digital logic levels. With input at 0 V, Q1 is turned on but is held out of saturation by Schottky diode D2. Resulting opamp gain is (R1 + R2)/R2.If R2 is 1.13 kilohms and R1 10 kilohms, gain is 10. When input is 5 V, Q1 is off and gate of Q2 is driven to -15 V. Gain now becomes (R1 + R2 + R3)/(R2 + R3). If R3 is 8.87 kilohms, gain is 2.-K. Karash, Gain-Programmable Amplifier, EEE Magazine, Sept. 1970, p 89.



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