Raytheon Company

Hughes Aircraft Company

Donald G McMullin

Lloyd Frederick Linder

Kelvin T Tran

Erick M Hirata

Benjamin Felder

Dwight D Birdsall

Roger N Kosaka

Phillip L Elliott

Hieu M Le

A current steering circuit diverts bias current from a differential current summing amplifier's front end when the differential input exceeds a safe threshold level, thus preventing the amplifier's output stage from being overdriven. Diverting the front end's bias currents also turns off transistors within the amplifier's front end and thus protects the front end from damage which may otherwise result from excessive input signals.

Current feedback differential amplifier clamp

First and second current feedback transconductance amplifiers (102,104) each have a high impedance voltage input, a low impedance current input and a pair of push-pull current outputs. In a single-ended configuration, an input signal is applied to the voltage input of the first transconductance amplifier (102) and the push-pull outputs of the both transconductance amplifiers are connected through a current mirror (136,138) to a node (134) where the current outputs are summed. The node current is integrated by a capacitor (174) to produce a voltage which is amplified by a transimpedance amplifier (190) to produce an output voltage which is fed back to the voltage input of the second transconductance amplifier (104). The current inputs of the transconductance amplifiers (102,104) are interconnected by a resistor (132). The high impedance voltage inputs produce common-mode cancellation of distortion in the transconductance amplifiers (102,104) and low input shot noise. In a differential configuration, differential input signals are applied to the voltage inputs of transconductance amplifiers (260,262), and a separate transimpedance amplifier (292,316) and current mirror (278,280) (302,304) is provided for each transconductance amplifier (260,262). A common-mode feedback circuit (352) controls the common-mode output voltages of the transimpedance amplifiers (292,316) to ground. Switch means (402,404,406,408,410,412) may be added to selectively ground the voltage inputs of the transconductance amplifiers (260,262) and disable their input stages by disconnecting their power supplies (VCC,VEE).

Single-ended and differential amplifiers with high feedback input

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Beverly Hills, CA, United States of America

Donald G McMullin