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Differential Input Amplifier

IP.com Disclosure Number: IPCOM000093135D
Original Publication Date: 1967-May-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Hollstein, CP: AUTHOR [+2]

Abstract

This differential input, signal-ended output amplifier circuitry permits the input terminals to move with common mode voltages. The feedback is referenced either to ground or to a point other than that of the input signal as desired.

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Differential Input Amplifier

This differential input, signal-ended output amplifier circuitry permits the input terminals to move with common mode voltages. The feedback is referenced either to ground or to a point other than that of the input signal as desired.

For the general case with plural input signals applied differentially to the base s of the plurality of paralleled transistor input circuits (out)=>(R(1)+R(2))/(R(2))|>E(1)(R(EF)/R(E1))+E(2)(R(EF)/R(E2)+
...E(N)(R(EF)/R(EN))|.

This arrangement is applicable to analog computing systems where the output voltage is useful in this form involving the ratios of feedback voltage divider impedance and emitter lead resistances of the individual circuits and the summing of the corresponding input voltages.

The input is isolated from the output by the high impedance of the reverse biased collector-base junctions of the input transistor pair. The circuitry has either well-matched transistors or the impedances of the resistors are chosen to operate the bipolar transistors at levels at which the mismatch is of negligible significance. In either case, a high input impedance can be maintained. Bias currents are balanced to minimize offset voltages.

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