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Remote Gain Control with Varistor

IP.com Disclosure Number: IPCOM000092631D
Original Publication Date: 1966-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

Braun, RJ: AUTHOR

Abstract

Amplifier 1 has its gain accurately controlled from a remote point. Varistor 2 is connected across the amplifier input so that bias current ldc produces an input voltage Vdc which is a logarithmic function of the current. Input signals produce a current Iac, which must be less than Idc, to produce a logarithmic change in input voltage Vac. The base emitter junction of 1 is an antilog device so that linear changes in Idc and Iac produce linear collector current changes in 1. Thus the amplitude of an output signal Vo is linearly controlled by a remote potentiometer R which produces the bias current source Idc.

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Remote Gain Control with Varistor

Amplifier 1 has its gain accurately controlled from a remote point. Varistor 2 is connected across the amplifier input so that bias current ldc produces an input voltage Vdc which is a logarithmic function of the current. Input signals produce a current Iac, which must be less than Idc, to produce a logarithmic change in input voltage Vac. The base emitter junction of 1 is an antilog device so that linear changes in Idc and Iac produce linear collector current changes in 1. Thus the amplitude of an output signal Vo is linearly controlled by a remote potentiometer R which produces the bias current source Idc.

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