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Fast Recovery Preamplifier

IP.com Disclosure Number: IPCOM000075617D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Swartz, JS: AUTHOR

Abstract

A b sampling the signal out of unbalance and applying a correction current. The correction current is applied to an emitter-coupled capacitor C, which is charged quickly to its operating point. Thus, the recovery current is made substantially zero and the amplifier operates in its normal mode.

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Fast Recovery Preamplifier

A b sampling the signal out of unbalance and applying a correction current. The correction current is applied to an emitter-coupled capacitor C, which is charged quickly to its operating point. Thus, the recovery current is made substantially zero and the amplifier operates in its normal mode.

Transistors Q1, Q2, Q3 and Q4 form an amplifier having a predetermined gain. The amplifier is AC coupled, to avoid differential input DC offset from affecting normal operation. The amplifier has a time constant in the emitter circuits that determines the recovery time.

In operation, when there is a large differential step between inputs 1 and 2, the capacitor C charges.through resistors R1 and R2. Transistors 9 and Q10 measure the offset of the differential input of the amplifier. The offset is amplified and applied to the bases of Q5, Q6 and Q7, Q8, and in turn the amplified signal is applied to the capacitor C to assist in charging the capacitor. As a result, the time constant is changed to a much shorter period, thus aiding the recovery time. Once recovery has been obtained, transistors Q9 and Q10 are switched off, and amplifier operation is obtained.

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