An RF transistor amplifier circuit comprises a Group III nitride based RF transistor amplifier having a gate terminal, a Group III nitride based self-bias circuit that includes a first Group III nitride based depletion mode high electron mobility transistor, the Group III nitride based self-bias circuit configured to generate a bias voltage, and a Group III nitride based depletion mode differential amplifier that is configured to generate an inverted bias voltage from the bias voltage and to apply the inverted bias voltage to the gate terminal of the Group III nitride based RF transistor amplifier. The Group III nitride based RF transistor amplifier, the Group III nitride based self-bias circuit and the Group III nitride based depletion mode differential amplifier are all implemented in a single die.

A system for adjusting bias power provided to a radio-frequency amplifier to increase plurality of figures of merit based on sensed characteristics of the amplifier and/or characteristics of the input or output power.

An output circuit includes a first transistor, a second transistor, an operational amplifier that outputs a control voltage, and a switch circuit that controls voltage output in accordance with a control signal. When the control signal is in a first state, the switch circuit supplies the control voltage to the gate of the first transistor to turn on the first transistor and electrically connects the drain of first transistor to the operational amplifier so that a first output voltage is output from the drain of the first transistor. When the control signal is in a second state, the switch circuit supplies the control voltage to the gate of the second transistor to turn on the second transistor and electrically connects the drain of the second transistor to the operational amplifier so that a second output voltage is output from the drain of the second transistor.

An envelope tracking power management circuit is disclosed. An envelope tracking power management circuit includes a first envelope tracking amplifier(s) and a second envelope tracking amplifier(s), each configured to amplify a respective radio frequency (RF) signal(s) based on a respective supply voltage. A power management circuit can determine that a selected envelope tracking amplifier, which can be either the first envelope tracking amplifier(s) or the second envelope tracking amplifier(s), receives the respective supply voltage lower than a voltage required to amplify the respective RF signal(s) to a predetermined voltage. In response, the power management circuit provides a boosted voltage, which is no less than the required voltage, to the selected envelope tracking amplifier. As such, it is possible to enable the selected envelope tracking amplifier to amplify the respective RF signal(s) to the predetermined voltage without increasing cost, footprint, and power consumption of the envelope tracking power management circuit.

An improved audio amplifier system can both reduce power consumption by supporting a standby mode and shorten wake time when resuming from the standby mode. The audio amplifier system may reduce power by entering a sleep or standby state in response to a command and/or detecting that an audio input signal is not received. Further, the audio amplifier system may use a burst generator to periodically or intermittently activate the power supply during standby mode. By periodically or intermittently activating the power supply, one or more of the capacitors may be charged. By charging the capacitors during standby mode, the time to wake from standby mode may be significantly reduced. In some cases, the wake time may be reduced by several order of magnitudes (e.g., from seconds to milliseconds).

A power amplification module includes: an amplifier that amplifies an input signal and outputs an amplified signal; and a harmonic-termination circuit to which harmonics of the amplified signal are input and the impedance of which is controlled in accordance with the frequency of a harmonic. The power amplification module can operate in a first mode in which a power supply voltage changes in accordance with the average voltage value of the amplified signal over a prescribed time period or in a second mode in which the power supply voltage changes in accordance with the envelope of the input signal. The impedance of the harmonic-termination circuit is controlled such that at least one even-ordered harmonic is short-circuited when the power amplification module operates in the first mode and at least one odd-ordered harmonic of third order or higher is short-circuited when the power amplification module operates in the second mode.

In accordance with embodiments of the present disclosure a control circuit may include at least one input for monitoring a respective signal for each of a plurality of amplifiers, an output for outputting at least one control signal for controlling a power supply level of the single signal-variant power supply configured to deliver electrical energy to the plurality of amplifiers, and decision and control logic. The decision and control logic may be configured to monitor the respective signals for each of the plurality of amplifiers and, based on the respective signals, and a respective requirement associated with each of the plurality of amplifiers, setting a power supply level of the single signal-variant power supply and outputting the at least one control signal to control the power supply level such that the respective requirements are satisfied.

Embodiments contained in the disclosure provide a method of cancelling power supply noise that affects the output of a class-D audio amplifier. The method begins when an alternating current (AC) coupled signal is input into an inverting amplifier. That signal is then amplified in the inverting amplifier. The amplified AC coupled signal is then feed through a resistor capacitor (RC) network, and from the RC network to an inverting input of the inverting amplifier. The output of a high pass filter is used to cancel the power supply ripple signal as the output of the high pass filter is injected into a supply voltage line. The cancelling signal is opposite in magnitude to the power supply ripple signal. The apparatus includes an inverting amplifier, a capacitor for coupling to an AC signal, and a resistor, in combination with the capacitor.

A variable-gain power amplifying technique includes generating, with a network of one or more reactive components included in an oscillator, a first oscillating signal, and outputting, via one or more taps included in the network of the reactive components, a second oscillating signal. The second oscillating signal has a magnitude that is proportional to and less than the first oscillating signal. The power amplifying technique further includes selecting one of the first and second oscillating signals to use for generating a power-amplified output signal, and amplifying the selected one of the first and second oscillating signals to generate the power-amplified output signal.

The invention relates to a technique for controlling in an envelope tracking amplification stage, comprising: determining a representation of the output signal of the amplifier; determining a representation of the input signal of the amplifier; adjusting the determined representation of the input signal according to a target characteristic of the amplifier; comparing the adjusted input and determined representation of the output; and generating a control signal in dependence on the comparison.