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Variable Gain Amplifier for AGC

IP.com Disclosure Number: IPCOM000096225D
Original Publication Date: 1963-Feb-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

Badal, FB: AUTHOR

Abstract

This is a variable gain amplifier for AGC. It comprises a transistor amplifier 10 whose emitter resistor 12 is shunted by a pair of oppositely poled diodes 14 and 16. Control voltage V(c) is supplied through diode 14. The circuit utilizes emitter degeneration controlled by voltage V(c) to vary its gain, given by the equation A--RL/RE where A = the gain and RL = the load resistance. RE is the equivalent resistance between the emitter and ground which is varied by variation of V(c) through changes in the slope of the composite diode curve.

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Variable Gain Amplifier for AGC

This is a variable gain amplifier for AGC. It comprises a transistor amplifier 10 whose emitter resistor 12 is shunted by a pair of oppositely poled diodes 14 and 16. Control voltage V(c) is supplied through diode 14. The circuit utilizes emitter degeneration controlled by voltage V(c) to vary its gain, given by the equation A--RL/RE where A = the gain and RL = the load resistance. RE is the equivalent resistance between the emitter and ground which is varied by variation of V(c) through changes in the slope of the composite diode curve.

This circuit can be connected to a full wave rectifier, a lowpass filter, and a suitable amplifier, the output of which comprises control voltage V(c).

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