An automatic gain control circuit controls a gain of a burst mode amplifier. A peak detector includes an input coupled to an output of the amplifier. A plurality of resistors is coupled in series between an input of the first amplifier and the output of the first amplifier for setting the gain of the amplifier. A first gain stage is responsive to an output signal of the peak detector for disabling a first resistor of the plurality of resistors to alter the gain of the first amplifier. A second gain stage is responsive to the output signal of the peak detector for disabling a second resistor of the plurality of resistors to alter the gain of the first amplifier. A comparator responsive to the output signal of the peak detector causes a pulse generator to enable the first gain stage and second gain stage each burst mode.

Techniques are described for using valley detection for supply voltage modulation in power amplifier circuits. Embodiments operate in context of a power amplifier circuit configured to be driven by a supply voltage generated by a supply modulator and to receive an amplitude-modulated (AM) signal at its input. The output of the power amplifier circuit can be fed to a valley detector that can detect a valley level corresponding to the bottom of the envelope of the AM signal. The detected valley level can be fed back to the supply modulator and compared to a constant reference. In response to the comparison, the supply modulator can vary the supply voltage to the power amplifier circuit in a manner that effectively tracking the envelope of the power amplifier circuit's output signal, thereby effectively seeking a flat valley for the output signal's envelope.

A power amplifier system having a power amplifier with a signal input and a signal output, bias circuitry coupled to the signal input, and a radio frequency (RF) peak detector having an input coupled to the signal output is disclosed. The RF peak detector is configured to generate a peak voltage signal. Temperature-compensated overvoltage protection circuitry coupled between an output of the RF peak detector and a control input of the bias circuitry is configured to respond to the peak voltage signal crossing over a predetermined peak voltage threshold and to provide an overvoltage protection control signal to cause the bias circuitry to adjust biasing for the power amplifier to reduce an overvoltage condition at the RF peak detector input.

A circuit comprises a sensing resistor with a resistance Rs, a first amplifier circuit with a first gain factor G, a second amplifier circuit with a second gain factor (1/A), a third amplifier circuit, a current mirror, a buffer, and a peak voltage detector. The first amplifier circuit is coupled to the sensing resistor at a first node and a second node and to the second amplifier circuit, which is further coupled to the current mirror. The buffer is coupled to the current mirror and to the third amplifier circuit, which is further coupled to the peak voltage detector and configured to receive a voltage across a load and a voltage on a ground node. In some implementations, the load is a speaker. In some implementations, a filter is coupled between the first and the second amplifier circuits.

Circuits and methods for reducing the cost and/or power consumption of a user terminal and/or the gateway of a telecommunications system (550) that may include a telecommunications satellite. Embodiments generate a dynamic input bias signal based upon an information signal envelope (which may be pre-distorted) which is applied to the signal input of a power amplifier (PA), thus reducing average power consumption. Other embodiments further include dynamic linearization (518) of the information signal, and/or variation of the supply voltage to the power amplifier (PA) as a function of the envelope of the information signal. Another aspect is a multi-stage chained feedback regulated voltage supply circuit for providing two or more output voltages that may be used as alternative supply voltages to a power amplifier (PA).

An audio amplifier includes: a buck controller configured to control an output voltage at a first supply terminal, the output voltage selected from a set including a plurality of output voltages, where the output voltage takes a settling time to settle; a first audio bridge including: a class-AB driver stage coupled to the first supply terminal, and a delay insertion circuit configured to receive a processed digital stream and provide the processed digital stream to the class-AB driver stage a delay time after receiving the processed digital stream, where the delay time is based on the settling time; and an audio amplitude detector configured to detect a first peak amplitude in the first digital audio stream, where the buck controller is configured to select a lowest output voltage from the set that is higher than the first peak amplitude plus a headroom voltage.

The invention relates to an amplification circuit (100), comprising: a VGA (2), an AGC loop (10) for automatically controlling the gain of the VGA (2), a switching circuit (14) for switching between an AGC mode, in which the gain of the VGA (2) is automatically controlled by an output signal of the AGC loop (10) and a manual gain control, MGC, mode, in which the gain of the VGA (2) can be manually controlled by an input signal, and a read/write circuit (30) with a contact (31) for connection to a peripheral system, wherein the read/write circuit (30) is configured, in the MGC mode, to provide the input signal from the contact (31) via a write-mode path (32) to the VGA (2), and, in the AGC mode, to provide the output signal of the AGC loop (10) via a read-mode path (33) on the contact (31).

A power amplifier with supply switching is provided. The power amplifier detects a magnitude of an outgoing broadband communication signal and determines whether the magnitude exceeds a predetermined voltage threshold. The power amplifier applies a first gain to the outgoing broadband communication signal using a first voltage supply rail when it is determined that the magnitude exceeds the predetermined voltage threshold and a second gain using a second voltage supply rail that is smaller than the first voltage supply rail when it is determined that the magnitude does not exceed the predetermined voltage threshold. The power amplifier produces an output signal from the outgoing broadband communication signal with the applied first gain or the applied second gain, wherein a current of the outgoing broadband communication signal is switched between the first voltage supply rail and the second voltage supply rail in response to the magnitude being detected.

An automatic gain control circuit controls a gain of a burst mode amplifier. A peak detector includes an input coupled to an output of the amplifier. A plurality of resistors is coupled in series between an input of the first amplifier and the output of the first amplifier for setting the gain of the amplifier. A first gain stage is responsive to an output signal of the peak detector for disabling a first resistor of the plurality of resistors to alter the gain of the first amplifier. A second gain stage is responsive to the output signal of the peak detector for disabling a second resistor of the plurality of resistors to alter the gain of the first amplifier. A comparator responsive to the output signal of the peak detector causes a pulse generator to enable the first gain stage and second gain stage each burst mode.

Peak voltage limiting circuits and method for power amplifiers. A power amplifier and/or a voltage limiting circuit includes a diode circuit coupled to an output of an amplification stage, the diode circuit configured to provide a conductive path from the output when an output voltage exceeds a selected value. The power amplifier and/or voltage limiting circuit also includes a sink circuit coupled to the diode circuit and a bias circuit, the sink circuit configured to reduce a bias voltage provided by the bias circuit when the output voltage exceeds the selected value to thereby limit the output voltage.