Amplifier circuit and method of amplifying a signal in an amplifier circuit

An audio amplifier circuit, comprising:

• an input, for receiving an audio input signal to be amplified;
• an envelope detector, for detecting the envelope of the input signal and adapted to output the detected input signal envelope to a switch select block;
• an amplifier for amplifying the audio input signal;
• and
• a charge pump for supplying one or more supply voltages to the amplifier, said charge pump comprising:
• an input for receiving a control signal;
• and
• a plurality of switches, wherein the plurality of switches comprises at least a first switch and a second switch that are connected in parallel, wherein said charge pump is configured to select said first switch and/or said second switch for use based on said control signal;
• wherein the control signal varies based on the detected envelope of the input signal, and wherein the input signal is modified by the volume control signal prior to the envelope detector detecting the audio input signal envelope.

An audio amplifier circuit, comprising:

• an input, for receiving an audio input signal to be amplified;
• an envelope detector, for detecting the envelope of the input signal and adapted to output the detected input signal envelope to a switch select block;
• an amplifier for amplifying the audio input signal;
• and
• a charge pump for supplying one or more supply voltages to the amplifier, said charge pump comprising:
• an input for receiving a control signal;
• and
• a plurality of switches, wherein the plurality of switches comprises at least a first switch and a second switch that are connected in parallel, wherein said charge pump is configured to select said first switch and/or said second switch for use based on said control signal;
• wherein the control signal varies based on the detected envelope of the input signal, and wherein the output from the envelope detector is modified by a volume control signal.

An audio amplifier circuit, comprising:

• an input, for receiving an audio input signal to be amplified;
• an envelope detector, for detecting the envelope of the input signal and adapted to output the detected input signal envelope to a switch select block;
• an amplifier for amplifying the audio input signal;
• and
• a charge pump for supplying one or more supply voltages to the amplifier, said charge pump comprising:
• an input for receiving a control signal;
• and
• a plurality of switches, wherein the plurality of switches comprises at least a first switch and a second switch that are connected in parallel, wherein said charge pump is configured to select said first switch and/or said second switch for use based on said control signal;
• wherein the control signal varies based on the detected envelope of the input signal, and wherein the control signal is modified by a volume control signal.

An audio amplifier circuit, comprising:

• an input, for receiving an audio input signal to be amplified;
• an amplifier for amplifying the audio input signal;
• and
• a charge pump for supplying one or more supply voltages to the amplifier, said charge pump comprising:
• an input for receiving a control signal;
• a plurality of switches, wherein the plurality of switches comprises at least a first switch and a second switch that are connected in parallel, wherein said charge pump is configured to select said first switch and/or said second switch for use based on said control signal;
• an input terminal for receiving an input voltage;
• first and second output terminals;
• first and second flying capacitor terminals;
• and
• a switch network for interconnecting said input terminal, said first and second flying capacitor terminals and said first and second output terminals to generate a first positive and a first negative output voltage that are each substantially equal in magnitude to half the magnitude of said input voltage.

An audio amplifier circuit, comprising:

• an input, for receiving an audio input signal to be amplified;
• an amplifier for amplifying the audio input signal;
• and
• a charge pump for supplying one or more supply voltages to the amplifier, said charge pump comprising:
• an input for receiving a control signal;
• a plurality of switches, wherein the plurality of switches comprises at least a first switch and a second switch that are connected in parallel, wherein said charge pump is configured to select said first switch and/or said second switch for use based on said control signal;
• an input terminal for receiving an input voltage;
• first and second output terminals;
• first and second flying capacitor terminals;
• and
• a switch network for interconnecting said input terminal, said first and second flying capacitor terminals and said first and second output terminals to generate either a first positive output voltage and a first negative output voltage that are each substantially equal in magnitude to the magnitude of the input voltage or a second positive output voltage and a second negative output voltage that are each substantially equal in magnitude to half the magnitude of said input voltage.