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Differential Amplifier

IP.com Disclosure Number: IPCOM000096158D
Original Publication Date: 1963-Jan-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Harnett, WT: AUTHOR

Abstract

The differential amplifier which is part of a servo system responds to an error signal to produce differential drive signals for correcting an unbalance or error condition in the servo loop. The error signal is supplied in form of an input potential difference to terminals A and B. The drive signals represented by currents 11 and 12 are utilized to feed load circuits, for instance, the coils of magnetic amplifiers.

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Differential Amplifier

The differential amplifier which is part of a servo system responds to an error signal to produce differential drive signals for correcting an unbalance or error condition in the servo loop. The error signal is supplied in form of an input potential difference to terminals A and B. The drive signals represented by currents 11 and 12 are utilized to feed load circuits, for instance, the coils of magnetic amplifiers.

The circuit has two branches 11 and 12 with provision for independent adjustment of the current flow through each branch of the circuit. The two branches are interconnected by the biasing networks 13 and 14. Each branch includes a PNP transistor 15 and 16. These are connected in common collector configuration to receive the differential input signals via terminals A and B. Each transistor 15 and 16 drives an associated NPN transistor 17 and 18, respectively, of its own branch through respective resistors 19 and 20. Each also controls the conductivity of the NPN transistor 18 and 17, respectively, of the opposite branch via cross connections 21 and 22.

In each of the branches the collector of the NPN transistor drives the load circuit 23 and 24, respectively, which is referenced to ground potential. Transistors 17 and 18 are connected in common base configuration to the biasing networks 13 and 14.

Each biasing network includes a potentiometer 25 and 26. These permit the quiescent current levels through each branch of the circuit to be independently adjusted to a particular level. Such is shown by the intersecting broken lines Y-Y' of the voltage...