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Differential Amplifier

IP.com Disclosure Number: IPCOM000076455D
Original Publication Date: 1972-Mar-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Decker, NH: AUTHOR

Abstract

Sensitivity to temperature differentials is avoided between the paired transistors of this differential amplifier. This is accomplished by maintaining the power dissipation of the differentially paired amplifiers constant regardless of the input signal.

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Differential Amplifier

Sensitivity to temperature differentials is avoided between the paired transistors of this differential amplifier. This is accomplished by maintaining the power dissipation of the differentially paired amplifiers constant regardless of the input signal.

Circuit inputs A and B are provided to transistors T1, T2 which act as both inverters and emitter-followers. In each instance, the emitter-follower connection is connected to a transistor of the differential pair, T3, T4. Driving of transistors T3, T4 is performed in a conventional manner. The inverter connection of T1 and T2 is made to transistors T5, T6 which establish the collector voltages of the differential pair through cascode stages. In this manner, the power dissipation of transistors T3 and T4 is maintained at a constant level, since the collector voltage of transistors T3 and T4 is decreased as driving transistors T1, T2 increase the current through the paired transistors.

Diodes D1, D2 limit the signal voltage differential applied to transistors T1, T2. Resistors R1, R2 in the emitter circuits of T3, T4 assure that these transistors are never cut off, thus reducing their power dissipation to zero. The action of these components is essential in guaranteeing constant-power dissipation in T3 and T4.

Transistors T3, T4 dissipate the same amount of power regardless of the state of unbalance of the differential amplifier. The circuit is normally operated in an unbalanced condition and...