A package or a chip including a linear amplifier and a power amplifier is provided, wherein the linear amplifier is configured to receive an envelope tracking signal to generate an amplified envelope tracking signal, the power amplifier is supplied by an envelope tracking supply voltage comprising a DC supply voltage and the amplified envelope tracking signal, and the power amplifier is configured to receive an input signal to generate an output signal.

A power supply switch circuit includes a switch circuit including a first switch configured to switch a first power source voltage to a power supply terminal of a power amplifier, and a second switch configured to switch a second power source voltage to the power supply terminal; a switch controller configured to control the switch circuit; and a power supply circuit configured to supply a third power source voltage to the power supply terminal when a first voltage of the power supply terminal is lower than a predetermined second voltage.

A power supply switch circuit includes a first transistor that switches supplying of a first power supply voltage to a power supply terminal of a power amplifier, a switch controller that controls the first transistor and to which a second power supply voltage is applied, and a voltage selector that selects a higher voltage among the first power supply voltage and the second power supply voltage. The selected higher voltage is applied to a body terminal of the first transistor or a gate terminal of the first transistor.

Certain aspects of the present disclosure are generally directed to circuitry and techniques for voltage-to-current conversion. For example, certain aspects provide a circuit for signal amplification including a first amplifier; a first transistor, a gate of the first transistor being coupled to an output of the first amplifier and a drain of the first transistor being coupled to an output node of circuit; a first resistive element coupled between a first input node of the circuit and an input of the first amplifier; a second amplifier; a second transistor, a gate of the second transistor being coupled to an output of the second amplifier and a drain of the second transistor being coupled to the output node of circuit; and a second resistive element coupled between a second input node of the circuit and an input of the second amplifier.

Apparatus and methods for envelope tracking systems with automatic mode selection are provided herein. In certain configurations, a power amplifier system includes a power amplifier configured to provide amplification to a radio frequency signal and to receive power from a power amplifier supply voltage, and an envelope tracker including a signal bandwidth detection circuit configured to generate a detected bandwidth signal based on processing an envelope signal corresponding to an envelope of the radio frequency signal. The envelope tracker further includes a switch bank configured to receive a plurality of regulated voltages, a filter configured to filter an output of the switch bank to generate the power amplifier supply voltage, and a mode control circuit configured to control a filtering characteristic of the filter based on the detected bandwidth signal.

A reconfigurable amplifier includes a first transistor having a gate coupled to an input of the reconfigurable amplifier, and a source coupled to a ground. The reconfigurable amplifier also includes a gate control circuit, and a second transistor having a gate coupled to the gate control circuit, a source coupled to a drain of the first transistor, and a drain coupled to an output of the reconfigurable amplifier, wherein the gate control circuit is configured to output a bias voltage to the gate of the second transistor in a cascode mode, and output a switch voltage to the gate of the second transistor in a non-cascode mode. The reconfigurable amplifier further includes a load coupled to the output of the reconfigurable amplifier.

An audio processing device includes a signal processing circuit, a power switch circuit, a power amplifier and a detection circuit. The signal processing circuit is configured to process an audio input to generate an audio signal. The power switch circuit is configured to generate an operating voltage. The power amplifier is coupled with the signal processing circuit and the power switch circuit, and configured to drive a load circuit by the operating voltage according to the audio signal. The detection circuit is coupled with the signal processing circuit and the power switch circuit, configured to obtain a volume value from the audio signal and compare the volume value with a first volume threshold to generate a comparison result, and configured to control, according to the comparison result, the power switch circuit to set the operating voltage to have a corresponding one of multiple voltage levels.

The audio amplification system comprises a power supply (100) connected to a feedback circuit (107), which is connected to the amplifier output filter, so that the power supply voltage (100) dynamically adjusts to the amplifier output voltage. Connected to the power supply (100) and mosfets (102) is a capacitor (108) with the function of stabilizing the power supply voltage (100). The system also comprises a control circuit (106), in which the mosfets (102) are connected, which connect to the output filter through an inductor (103) and a capacitor (104). The amplifier output (101) involves a speaker (105).

A symbol-power-tracking (SPT) voltage supply to power a radio-frequency power amplifier (RF PA) is shown. A power converter is coupled to an output port of an input power source for power conversion, and has an output terminal coupled to a power terminal of the RF PA. A transition capacitor is coupled to the power terminal of the radio-frequency power amplifier through the output terminal of the power converter. An assisted charging and discharging circuit is coupled to the transition capacitor during cyclic prefix (CP) sections. A multi-level array is provided which includes a plurality of voltage-regulated capacitors pre-charged to and kept at different voltage levels. During each symbol section, a target capacitor at a fixed voltage level matching the current SPT situation is selected from among the voltage-regulated capacitors to be coupled to the power terminal of the radio-frequency power amplifier.

A signal amplifying circuit and associated methods and apparatuses, the circuit comprising: a signal path extending from an input terminal to an output terminal, a gain controller arranged to control the gain applied along the signal path in response to a control signal; an output stage within the signal path for generating the output signal, the output stage having a gain that is substantially independent of its supply voltage, and a variable voltage power supply comprising a charge pump for providing positive and negative output voltages, the charge pump comprising a network of switches that is operable in a number of different states and a controller for operating the switches in a sequence of the states so as to generate positive and negative output voltages together spanning a voltage approximately equal to the input voltage.