Tektronix, Inc.

Frank G DiGiovanni

John L Addis

Davorin Fundak

A differential amplifier includes two amplifier halves each including a feedback transistor for providing closed-loop gain, for driving a common load impedance, and for providing a differential current output. Each amplifier half further includes a first feedback path operable in a normal operating condition and a second feedback path operable in an overdrive condition. The first feedback path consists of first and second diodes connected between an emitter of the feedback transistor and a voltage input of the differential amplifier. A junction between the first and second diodes is coupled to the common load impedance. The second feedback path consists of a third diode connected between the emitter of the feedback transistor and the second voltage input, such that the differential amplifier and the feedback transistor remain operational and electrically isolated from the load impedance during the overdrive condition. Once the overdrive condition is removed, the first feedback path again becomes operational, and the amplifier quickly recovers without saturation or thermally induced errors. A minimum number of circuit elements is required for overdrive recovery including three diodes and a current source for biasing the third diode in the overdrive condition.

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Portland, OR, United States of America

Frank G DiGiovanni