An amplifier for modulating the amplitude of an RF signal, the amplifier including: a plurality of amplifier circuits, each circuit being connected to a first power source, each circuit including a charge storage device and an output across which a potential difference supplied by the first power source can be applied; a switching arrangement for switching connections between the first power source, the charge storage device, and the output in each amplifier circuit, wherein each circuit includes a first switched configuration in which the charge storage device is charged by the first power source and a second switched configuration in which the charge storage device, once charged, will apply an additional potential difference across the output. The amplifier is configured to vary the amplitude of the RF signal in proportion to the sum of the potential differences applied across the output in each amplifier circuit.

This application relates to Class D amplifier circuits (200). A modulator (201) controls a Class D output stage (202) based on a modulator input signal (Dm) to generate an output signal (Vout) which is representative of an input signal (Din). An error block (205), which may comprise an ADC (207), generates an error signal () from the output signal and the input signal. In various embodiments the extent to which the error signal () contributes to the modulator input signal (Dm) is variable based on an indication of the amplitude of the input signal (Din). The error signal may be received at a first input (204) of a signal selector block (203). The input signal may be received at a second input (206) of the signal selector block (203). The signal selector block may be operable in first and second modes of operation, wherein in the first mode the modulator input signal is based at least in part on the error signal; and in the second mode the modulator input signal is based on the digital input signal and is independent of the error signal. The error signal can be used to reduce distortion at high signal levels but is not used at low signal levels and so the noise floor at low signal levels does not depend on the component of the error block (205).

A transimpedance amplifier (TIA) structure includes an input node with a variable inductance component serving to reduce variation in peak amplitude over different gain conditions. According to certain embodiments, an inductor at the TIA input has a first node in communication with a Field Effect Transistor (FET) drain, and a second node in communication with the FET source. A control voltage applied to the FET gate effectively controls the input inductance by adding a variable impedance across the inductor. Under low gain conditions, lowering of inductance afforded by the control voltage applied to the FET reduces voltage peaking. TIAs in accordance with embodiments may be particularly suited to operate over a wide dynamic range to amplify incoming electrical signals received from a photodiode.

A driver that drives an optical device, such as laser diode (LD) and/or optical modulator, is disclosed. The driver includes a variable gain amplifier (VGA) and a post amplifier. The post amplifier amplifies an output of the VGA to a preset amplifier as varying the gain of the VGA. The VGA includes two differential pairs each amplify the input signal oppositely in phases thereof and outputs of the differential pairs are compositely provided to the post amplifier. The gain of the VGA is varied by adjusting contribution of the second differential pair to the output of the VGA.

Circuits and operating methods thereof for correcting phase errors introduced by amplifiers employing gallium nitride (GaN) transistors are described. The phase errors are caused by trapping effects exhibited by the GaN transistors. The circuits described herein pre-distort the phase of the input signal to compensate for the phase error introduced by the amplifier. Thereby, the phase of the output signal of the amplifier has a reduced phase error. For example, the output signal may have a near zero (or zero) phase error.

This application relates to Class D amplifier circuits (200). A modulator (201) controls a Class D output stage (202) based on a modulator input signal (Dm) to generate an output signal (Vout) which is representative of an input signal (Din). An error block (205), which may comprise an ADC (207), generates an error signal () from the output signal and the input signal. In various embodiments the extent to which the error signal () contributes to the modulator input signal (Dm) is variable based on an indication of the amplitude of the input signal (Din). The error signal may be received at a first input (204) of a signal selector block (203). The input signal may be received at a second input (206) of the signal selector block (203). The signal selector block may be operable in first and second modes of operation, wherein in the first mode the modulator input signal is based at least in part on the error signal; and in the second mode the modulator input signal is based on the digital input signal and is independent of the error signal. The error signal can be used to reduce distortion at high signal levels but is not used at low signal levels and so the noise floor at low signal levels does not depend on the component of the error block (205).

A transimpedance amplifier (TIA) structure includes an input node with a variable inductance component serving to reduce variation in peak amplitude over different gain conditions. According to certain embodiments, an inductor at the TIA input has a first node in communication with a Field Effect Transistor (FET) drain, and a second node in communication with the FET source. A control voltage applied to the FET gate effectively controls the input inductance by adding a variable impedance across the inductor. Under low gain conditions, lowering of inductance afforded by the control voltage applied to the FET reduces voltage peaking. TIAs in accordance with embodiments may be particularly suited to operate over a wide dynamic range to amplify incoming electrical signals received from a photodiode.

A transimpedance amplifier (TIA) structure includes an input node with a variable inductance component serving to reduce variation in peak amplitude over different gain conditions. According to certain embodiments, an inductor at the TIA input has a first node in communication with a Field Effect Transistor (FET) drain, and a second node in communication with the FET source. A control voltage applied to the FET gate effectively controls the input inductance by adding a variable impedance across the inductor. Under low gain conditions, lowering of inductance afforded by the control voltage applied to the FET reduces voltage peaking. TIAs in accordance with embodiments may be particularly suited to operate over a wide dynamic range to amplify incoming electrical signals received from a photodiode.

A high-frequency power supply (10) uses one pulse conversion/variable gain amplification unit (23) to perform two processing steps which are converting an RF signal into pulses and controlling an output level, and uses one control signal (27) to perform the pulse conversion and the output level control by the pulse conversion/variable gain amplification unit (23), thereby obviating the need for a modulation unit, which is a factor in the generation of jitter, overshoot, and undershoot, and reducing the number of control lines (29) for sending the control signal (27) to one control line. Due to this configuration, the jitter, overshoot, and undershoot generated in an RF pulse signal can be prevented, and the RF-signal pulse conversion and output level control are performed simultaneously using one control line (29).

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.