A power amplifier includes an output signal generator constructed to generate, on the basis of an input AC signal, an output signal including, in cycles, a first pulse being width higher in voltage than a first reference voltage and a second pulse being width lower in voltage than the first reference voltage and a feedback circuit constructed to generate a first bias signal corresponding to the output signal and feed back the first bias signal to an input side of the output signal generator to equalize a width of the first pulse and a width of the second pulse in the cycles of the output signal.

In one aspect, a power amplifier apparatus comprising a power amplifier (PA) and an adaptive controller is provided. The PA comprises at least one transistor and the adaptive controller is configured to control a bias voltage of the transistor based on a measured power efficiency of the PA and a measure output signal quality of the PA. In another aspect, a method of optimizing PA performance is provided. The PA comprises at least one transistor and the method includes initializing a bias voltage of the transistor, receiving measurements indicating a power efficiency and an output signal quality of the PA, evaluating the received measurements, calculating a new bias voltage for the transistor based on the evaluation, and applying the calculated new bias voltage to the transistor.

A power amplifier (20) for a transmitter circuit (10) is disclosed. The power amplifier (20) comprises at least one field-effect transistor (100, 100n, 100p) having a gate terminal (110, 110n, 110p) and a bulk terminal (120, 120n, 120p), wherein the at least one field-effect transistor (100, 100n, 100n) is configured to receive an input voltage at the gate terminal (110, 110p, 110n) and a dynamic bias voltage at the bulk terminal (120, 120n, 120p). Furthermore, the power amplifier (20) comprises a bias-voltage generation circuit (130). The input voltage is a linear function of an input signal. The bias-voltage generation circuit (130) is configured to generate the dynamic bias voltage as a nonlinear function of an envelope of the input signal.

Apparatus and methods for LNAs with mid-node impedance networks are provided herein. In certain configurations, an LNA includes a mid-node impedance circuit including a resistor and a capacitor electrically connected in parallel, a cascode device electrically connected between an output terminal and the mid-node impedance circuit, and a transconductance device electrically connected between the mid-node impedance circuit and ground. The transconductance device amplifies a radio frequency signal received from an input terminal. The LNA further includes a feedback bias circuit electrically connected between the output terminal and the input terminal and operable to control an input bias voltage of the transconductance device.

A circuit includes first and second gain stages and an output transistor. The second gain stage includes a transconductance amplifier and a variable impedance circuit coupled to an output of the transconductance amplifier. The variable impedance circuit is configured to implement a first impedance level at frequencies below a first frequency threshold and to implement a second impedance level at frequencies above a second frequency level. The first impedance level is larger than the second impedance level. The output transistor has a control input coupled to the variable impedance circuit. At frequencies above the second frequency threshold, the second impedance level is configured to be inversely related to current through the output transistor.

A circuit includes first and second gain stages and an output transistor. The second gain stage includes a transconductance amplifier and a variable impedance circuit coupled to an output of the transconductance amplifier. The variable impedance circuit is configured to implement a first impedance level at frequencies below a first frequency threshold and to implement a second impedance level at frequencies above a second frequency level. The first impedance level is larger than the second impedance level. The output transistor has a control input coupled to the variable impedance circuit. At frequencies above the second frequency threshold, the second impedance level is configured to be inversely related to current through the output transistor.

Devices and methods for generating a bias voltage for a transceiver operating in time division multiplexing operation, and corresponding transceivers are provided. In this case, the bias voltage is controlled in guard intervals between transmission and reception of signals by the transceiver.

A power amplifier circuit includes a first transistor, a second transistor and a bias circuit. The first transistor has a base configured to receive a first signal. The second transistor has an emitter connecting to a collector of the first transistor and a collector configured to output a second signal. The bias circuit is coupled to the first transistor and the second transistor. The bias circuit is configured to provide a direct current (DC) voltage at the collector of the second transistor about twice a DC voltage at the collector of the first transistor. The bias circuit is configured to provide an alternating current (AC) or radio frequency (RF) voltage at the collector of the second transistor about twice an AC or RF voltage at the collector of the first transistor.

In one embodiment, an LDO circuit is configured to increase a bias current to an error amplifier of the LDO circuit, and to subsequently return the bias current to an earlier value in response to the output current increasing to greater than a threshold current level.

An apparatus comprises a plurality of selectable gain stages connected in parallel between a first bias voltage and ground, wherein each selectable gain stage comprises an amplification portion and a current steering portion, and wherein the current steering portion comprises a first selectable signal path connected between an output of the amplification portion and a signal output terminal, and a second selectable signal path connected between the output of the amplification portion and ground through a shunt device.