Tektronix, Inc.

Macom Technology Solutions Holdings, Inc.

Mindspeed Technologies, Inc.

Michael P Khaw

Daniel G Knierim

Daniel Draper

Theodore G Nelson

Clifford E Baker

John F Stoops

A transimpedance amplifier that includes an input configured to receive a current input from an upstream device and output configured to present an output voltage. The current input may be from a photodetector or any other device that is part of an optical signal receiving unit front end. In one configuration, there are three amplifier stages in the transimpedance amplifier connected in series. A feedback path with feedback resistor connects between the input and output of the transimpedance amplifier. A bandwidth extender circuit connects between a stage output and a stage input of the transimpedance amplifier. In a three stage embodiment, the bandwidth extender circuit extends between an input of the second stage and the output of the second stage. The bandwidth extender includes at least one active device configured to provide positive feedback to increase gain. The bandwidth extender circuit is able to be automatically or selectively deactivated to filter unwanted frequency components.

Transimpedance amplifier with bandwidth extender

In one system embodiment, the system is characterized by: a differential amplifier including but not limited to at least one amplifying transistor having an emitter coupled directly to a ground. In one embodiment of a method of making a system, the method is characterized by: operably coupling at least one amplifying transistor of a differential amplifier directly to a ground. In one embodiment of a method of driving a system, the method is characterized by: driving at least one amplifying transistor of a differential amplifier with an emitter-follower feedback loop. In one system embodiment, the system is characterized by: a differential amplifier including but not limited to a first amplifying transistor having a base operably coupled with a first emitter-follower feedback loop.

Driver circuits and methods

A high impedance attenuator for use in a test and measurement instrument employs compensation to adjust the low frequency attenuation to match the high frequency attenuation exhibited by the attenuator, rather than attempting to adjust the high frequency attenuation exhibited by the attenuator. In an alternate embodiment of the invention, compensation to adjust low frequency attenuation is employed in a feedback loop and an opposite compensation is applied in a parallel attenuation stage to stabilize the input resistance. In yet another embodiment of the invention, compensation to adjust low frequency attenuation is employed by means of an R-C time constant of an additional R-C circuit in a feed forward loop. This additional time constant is matched to the R-C time constant of the input R-C network. The input resistance of the attenuator is not changed.

Apparatus and method for compensating a high impedance attenuator

A split-path isolation amplifier (10) employs a transformer (30) in a high path (26) and a single-input, dual-output closed-loop optocoupler (66) in a low path (24) to achieve a flat, wide frequency response without need for frequency compensation adjustments. In a low path frequency region (106), the optocoupler provides all or most of the signal to the output. The isolation amplifier employs a substantially overlapped crossover frequency region (104) in which the high path signal is applied to a primary winding (28) of the transformer, and the low path signal is applied differentially to secondary windings (40, 42) of the transformer. At frequencies below the crossover frequency range, the signal from the optocoupler dominates as the signal coupled from the primary winding rolls off. At frequencies above the crossover frequency range, the signal coupled from the primary winding dominates as the signal from the optocoupler rolls off. At frequencies within the crossover frequency range magnetic flux components generated by the primary and secondary transformer windings co-act to provide a combined output signal having a flat frequency response. The only adjustments are those required to match the gain of the low path to the gain of the high path and to compensate for any offset in the low path.

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Portland, OR, United States of America

Michael P Khaw