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Logic Controlled Analog Amplifier

IP.com Disclosure Number: IPCOM000079720D
Original Publication Date: 1973-Aug-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Buhler, OR: AUTHOR

Abstract

These analog amplifiers selectively provide a gain of plus one or minus one, in accordance with the binary state of a control signal. This is accomplished by adding one resistor and one binary control switch to a conventional inverting amplifier.

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Logic Controlled Analog Amplifier

These analog amplifiers selectively provide a gain of plus one or minus one, in accordance with the binary state of a control signal. This is accomplished by adding one resistor and one binary control switch to a conventional inverting amplifier.

Switch 10, Fig. 1, provides the binary control signal function and may be a switching transistor or the contacts of a relay. When switch 10 is open, as shown, operational amplifier 11 is connected as a modified voltage follower, the modification being the presence of resistors 12, 13 and 14, wherein the input/output gain is plus one, independent of resistor values. When switch 10 is closed, amplifier 11 is connected as an inverting amplifier, wherein the input/output gain is minus one, the magnitude of resistors 13 and 14 determining the gain. When resistor 13 is equal to resistor 14, the gain is minus one.

In Fig. 2, switch 10 has two operating positions. In position 15 the gain is plus one. In position 16 the gain is minus one. This circuit has the advantage of reducing output offset by bias current cancellation.

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