A low distortion transconductance amplifier provides current to a grounded load using a virtual ground input stage, a pair of current mirrors, and a bias current source. The virtual ground input stage may include transistors arranged as a Darlington pair. The low distortion transconductance amplifier can function as a voltage-controlled AC current source that is operable at high frequencies.

A class D amplifier output stage including an input for receiving an input signal, an output for providing an output signal to a load, serially coupled upper and lower switching devices configured to provide an output signal to the output, a driver circuit configured to receive the input signal, and to derive therefrom first and second drive signals for driving the upper and lower switching devices alternately from a conducting state into a non-conducting state and vice versa, such that the conducting state periods of the upper switching device with respect to those of the lower switching device are mutually exclusive and separated by dead time intervals during which both upper and lower output transistors are non-conducting. To reduce distortion and more particularly, total harmonic distortion (THD), the amplifier output stage includes a substantially linear circuit configured to provide a bidirectional current sink for residual currents from the load occurring during at least part of each dead time interval.

An audio reproduction apparatus is shown and includes an amplifier with a power amplification stage having transistors in a push-pull arrangement. A bias generator biases the transistors with a standing current. A processor receives a data stream comprising digital samples of an analog audio signal and analyzes the peak level of each group. It then determines the appropriate standing currents to maintain Class A operation of the power amplification stage given the peak levels of each of the groups. A digital to analog converter produces an analog input signal for the input stage of the amplifier from the data stream. A feedforward path between the processor and the bias generator allows the standing current to be adjusted prior to the arrival of the analog input signal in the power amplification stage.

An inductor-less low noise amplifier (LNA) with high linearity is disclosed. The low noise amplifier includes: an input signal stage receiving an input signal; a first amplifier configured to receive the input signal, generate a first amplification signal by amplifying the received input signal, and output the generated first amplification signal, as a first output signal, to a first output terminal; a second amplifier configured to receive the input signal, generate a second amplification signal by amplifying the received input signal, and output the generated second amplification signal, as a second output signal, to a second output terminal; an output signal stage outputting a superimposition signal obtained by superimposing the first output signal and the second output signal; a first resistor feeding back the superimposition signal to the input signal stage; and a switch connecting/disconnecting between the input signal stage and the output signal stage.

An integrated circuit comprises a first amplifier circuit with a push-pull amplifier configured to be calibrated to a low second order distortion. The integrated circuit further comprises a second amplifier circuit with at least one push-pull amplifier, wherein a size ratio between sizes of the transistors is adjustable by adjusting the size of at least one transistor device. The size ratio can be consecutively adjusted to a plurality of values, and for each value, a first output signal of a push-pull amplifier with an applied test signal and a second output signal of a push-pull amplifier without applied test signal, are determined. The size ratio for which a difference between the push-pull amplifier output signals is closest to zero is determined, and the push-pull amplifier of the first amplifier circuit is calibrated in dependence of the determined size ratio.

Systems and methods for amplifying signals. In some embodiments, the signals may be amplified using a diode steering network with an amplifier operated in class AB mode. In some embodiments, distortion in the amplified signal may be corrected using a feed forward cancellation circuit operated in class A mode.

An amplifier comprising a main branch amplifier and an auxiliary branch amplifier, wherein one branch is a constant current-biased branch, and another branch is a voltage biased branch, with the branches connected in cascode configuration to form a load modulated amplifier.

A signal amplifying circuit includes an amplifier and a common mode feedback circuit. The amplifier generates first and second outputs. The common mode feedback circuit receives the first and second outputs, and controls an output common mode voltage of the first and second outputs to a first reference voltage. The common mode feedback circuit includes an output common mode voltage detection circuit, a pull-up circuit and a pull-down circuit. The output common mode voltage detection circuit generates first and second control signals according to the output common mode voltage. The pull-up circuit with a first conduction degree controlled by the first control signal controls the output common mode voltage to be positively correlated with the first conduction degree. The pull-down circuit with a second conduction degree controlled by the second control signal controls the output common mode voltage to be negatively correlated with the second conduction degree.

Disclosed is a power amplifier system having a main amplifier with an input coupled to a main radio frequency (RF) input and an output connected to a main RF output, wherein the main amplifier exhibits a nonlinear gain characteristic with compression. At least one compression compensating amplifier has a signal input coupled to the common RF input and a signal output coupled to the common RF output.

An amplifier circuit is disclosed. The amplifier circuit includes an input terminal configured to receive an input signal, an output terminal configured to transmit an output signal, and a first signal path including a first amplifying circuit, where the first amplifying circuit is configured to receive the input signal and to transmit a first amplified output to the output terminal, and where the first amplified output includes first amplifier circuit harmonic noise. The amplifier circuit also includes a second signal path including a second amplifying circuit, where the second amplifying circuit receives the input signal and transmits a second amplified output to the output terminal, and where the second amplified output includes second amplifier circuit harmonic noise. The output signal includes the first and second amplified outputs, and the first amplifying circuit harmonic noise is at least partially canceled by the second amplifying circuit harmonic noise in the output signal.