A voltage gain amplifier (VGA) configured to have reduced supply noise. The VGA includes first resistor, first FET, and a first current-source coupled between first and second voltage rails. The VGA includes second resistor, second FET, and second current-source coupled between the voltage rails. A variable resistor is coupled between the respective sources of the first and second FETs. Variable capacitors are coupled between the first or a third voltage rail and the sources of the first and second input FETs, respectively. If capacitors are coupled to the first voltage rail, noise cancellation occurs across the gate-to-source voltages of the FETs if an input differential signal applied to the gates of the FETs is derived from a supply voltage at the first voltage rail. If capacitors are coupled to the third rail, supply noise is reduced if the supply voltage at the third rail is generated by a cleaner regulator.

The disclosure relates to a system and method for controlling a common mode voltage of an output differential signal of a differential signal processing circuit using a replica circuit and feedback control. The differential signal processing circuit includes two load devices, two input transistors, and two current-source transistors coupled in series between voltage rails, respectively. The replica circuit includes replica load device, replica input transistor, and replica current-source transistor coupled in series between the voltage rails. The common mode voltage of the input differential signal is applied to the replica input transistor to generate a replica output common mode voltage. A feedback circuit generates a bias voltage for the replica current-source transistor and the current-source transistors of the differential circuit to set and control the replica output common mode voltage and the output common mode voltage of the differential signal processing circuit to a target common mode voltage.

An amplifier, a circuit, and an optical communication system are provided. The disclosed amplifier may include a first transistor receiving a first portion of an input signal received at the amplifier, a second transistor receiving a second portion of the input signal, an automatic gain control signal that is dynamically adjustable in response to variations in an output of the amplifier, and a varactor that has its capacitance adjusted by changes in the automatic gain control signal and, as a result, adjusts a position of a pole in a transfer function of the amplifier.

An optical communication system, a linear optical receiver, and an Integrated Circuit (IC) chip are disclosed, among other things. One example of the disclosed IC chip includes a transimpedance amplifier that receives an input electrical signal from a photodiode and provides an amplified version of the input electrical signal as an output, at least one variable gain amplifier that receives the amplified electrical signal output by the transimpedance amplifier and a bandwidth control mechanism that extends a bandwidth of the second amplified output at a maximum gain of the second amplification phase and also reduces a peaking of the second amplified output at a minimum gain of the second amplification phase.

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 3 dB bandwidth ranging from 1 GHz to 60 GHz with a widened gain control range up to 12 dB without increasing power consumption.

Methods and systems for a configurable low-noise amplifier with programmable band-selection filters may comprise a receiver with a low-noise amplifier (LNA) with differential output terminals; a low pass filter operably coupled to the LNA; a high pass filter operably coupled to the second input terminal of the LNA; and a signal source input coupled to the low pass filter and the high pass filter. The LNA may be operable to receive signals in a pass band of the high pass filter and a pass band of the low pass filter. The receiver may be operable to amplify input signals in the pass band of a first filter but not signals in the pass band of the second filter by operably coupling the second to ground.

Methods and systems for a configurable low-noise amplifier with programmable band-selection filters may comprise a receiver with a low-noise amplifier (LNA) with differential output terminals; a low pass filter operably coupled to the LNA; a high pass filter operably coupled to the second input terminal of the LNA; and a signal source input coupled to the low pass filter and the high pass filter. The LNA may be operable to receive signals in a pass band of the high pass filter and a pass band of the low pass filter. The receiver may be operable to amplify input signals in the pass band of a first filter but not signals in the pass band of the second filter by operably coupling the second to ground.

Certain aspects of the present disclosure provide methods and apparatus for adjusting a bandwidth of an amplifier (e.g., a programmable gain amplifier (PGA)). In certain aspects, the PGA generally includes at least one amplification stage having an input and an output, a plurality of compensation capacitors, and at least one first switch configured to selectively couple at least one capacitor of the plurality of compensation capacitors between the input and the output of the at least one amplification stage. In certain aspects, the amplifier includes at least one second switch configured to selectively couple the at least one capacitor to a node such that the at least one capacitor is coupled to only one of the output or the node, where a voltage at the node is a differential mode (DM) reference potential for the amplification stage.

A radio frequency (RF) receiver that includes a low noise amplifier (LNA), a tunable resonant circuit, and a processor for performing calibration of the RF receiver. The processor is configured to sweep the tunable resonant circuit through a dynamic range of resonant frequency settings while estimating noise signal output power at the LNA at each setting. The processor is also configured to set the tunable resonant circuit to the setting that produces the greatest noise signal power output at the LNA.

Provided is a reconfigurable amplifier. The reconfigurable amplifier includes a gain circuit including a gain path configured to amplify an input signal, and a feed forward circuit including a feed forward path configured to receive the input signal and perform feed forward compensation on the input signal, and a first control circuit configured to perform the feed forward compensation in a first mode by activating the feed forward path, and deactivate the feed forward path in a second mode different from the first mode.