Inphi Corporation

Subramaniam Shankar

Steffen O Nielsen

Ariel Leonardo Vera Villarroel

Carl W Pobanz

A circuit for blocking undesired input direct current of AC-coupled broadband circuits. The circuit includes a capacitor coupled to an input port and a common node. The input port receives a RF input signal. Additionally, the circuit includes a current source supplying a DC current to the common node leading a bias current to an output port. Further, the circuit includes a variable voltage source through an internal load and a close loop with an application circuit having an input load coupled to the output port to determine various bias voltages to control the bias current at the output port in association with a RF output signal that is substantially free of any input direct current originated from the RF input signal and is associated with an inherent low cut-off frequency independent of the various bias voltages.

DC blocking circuit with bias control and independent cut-off frequency for AC-coupled circuits

A variable gain amplifier having stabilized frequency response for widened gain control range. A resistor-capacitor compensation network is provided between two differential current input ports and corresponding emitter nodes of cross-coupled four transistors in the variable gain amplifier to desensitize the gain control voltages to the system noise and provide compensation to the VGA frequency response when the differential gain control voltage varies the gain setting, yielding a substantially stabilized frequency response over a &#x2212;3 dB bandwidth ranging from 1 GHz to 60 GHz with a widened gain control range up to 12 dB without increasing power consumption.

Variable gain amplifier with stable frequency response

The present disclosure provides a detailed description of techniques for implementing a linear amplifier with extended linear output range. More specifically, the present disclosure discloses techniques for extending the output signal range of a linear amplifier with a minimum increase in power consumption and die area consumption. Some embodiments facilitate coupling boost amplifiers with adjustable independent biasing to a main amplifier to boost the output signal near the non-linear regions of the transfer curve to extend the linear range. Certain embodiments comprise a first boost amplifier biased to contribute to the output signal when the input signal is near a negative threshold voltage, and a second boost amplifier biased to contribute to the output signal when the input signal is near a positive threshold voltage. In certain embodiments, the threshold voltages and/or the bias currents can be controlled to adjust certain amplifier attributes.

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Thousand Oaks, CA, United States of America

Subramaniam Shankar