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An Immediate Acting Automatic Gain Control Circuit

IP.com Disclosure Number: IPCOM000096406D
Original Publication Date: 1963-May-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Hanson, CC: AUTHOR [+2]

Abstract

An input signal e in is applied to input terminal 10. This signal is amplified by amplifier 11. The first peak of the signal is stored in capacitor C. The current from capacitor C is a control current and it is fed to two forwardly biased diodes D1 and D2.

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An Immediate Acting Automatic Gain Control Circuit

An input signal e in is applied to input terminal 10. This signal is amplified by amplifier 11. The first peak of the signal is stored in capacitor C. The current from capacitor C is a control current and it is fed to two forwardly biased diodes D1 and D2.

The current flowing through resistor R1 due to the peak signal stored in capacitor C causes the signal resistance of D1 to vary inversely proportional to this current. Similarly, the current flowing through resistor R2 due to the peak signal stored by C causes the signal resistance of D2 to vary inversely proportional to this current. A change in signal level stored by C causes transients to appear at the anodes D1 and D2. These transients normally would be much greater than the input signal e in. To eliminate the transient effect, the two transient signals are fed to a differential amplifier 15. By this arrangement, the signal appear s at output terminal 16 of amplifier 15 with little or no transient effect.

The output of amplifier 15 is designated e0 and it is equal to e1 minus e2 times the amplifier gain. In this instance, e1 equals K(e in)/ Ic + transient voltage et and e2 equals transient voltage et. K is a constant in the range where the dynamic resistance of diodes D1 and D2 is linear. Therefore, e0 equals G K (e in)/Ic where G is the gain amplifier 15 and Ic is the control current from C.

Two input and output voltage wave forms are shown. The voltage wa...