Audio amplifier circuit and electronic apparatus including the same
First Claim
1. An audio amplifier circuit for amplifying an input signal to produce an output signal for driving a load, wherein said circuit is configured to operate:
- in a first mode when directly driving an audio output transducer andin a second mode when driving a line input of an external amplifying apparatus, wherein the output signal produced in the second mode has a higher voltage amplitude for a given signal content than the output signal produced in the first mode;
wherein the circuit comprises common output stage circuitry for use in both modes, and a dual mode power supply circuit for supplying said output stage in the first mode with a lower supply voltage than in the second mode.
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Accused Products
Abstract
An electronic audio amplifier circuit, operable in two modes and a battery powered portable audio apparatus incorporating the circuit; and associated apparatuses and methods. When in the first mode the audio apparatus is designed for the direct driving of headphones or a speaker. When in the second mode the audio apparatus is designed to drive a line input of an external amplifying apparatus with a signal that having a higher voltage amplitude for a given signal content than when driving headphone or a speaker. The circuit has common output stage circuitry for use in both modes, and a dual mode power supply circuit, ideally a charge pump circuit, for supplying the output stage in the first mode with a lower supply voltage than in the second mode.
75 Citations
37 Claims
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1. An audio amplifier circuit for amplifying an input signal to produce an output signal for driving a load, wherein said circuit is configured to operate:
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in a first mode when directly driving an audio output transducer and in a second mode when driving a line input of an external amplifying apparatus, wherein the output signal produced in the second mode has a higher voltage amplitude for a given signal content than the output signal produced in the first mode; wherein the circuit comprises common output stage circuitry for use in both modes, and a dual mode power supply circuit for supplying said output stage in the first mode with a lower supply voltage than in the second mode. - View Dependent Claims (2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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5. An apparatus as claimed in 4 wherein the supply voltage in the second mode is also split either side of said ground reference.
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28. An electronic audio amplifier circuit operable in two modes:
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a first mode for the direct driving of an audio output transducer and a second mode to drive a line input of an external amplifying apparatus, an output signal to be provided to said line input in the second mode having a higher voltage amplitude for a given signal content than an output signal driving said audio output transducer; wherein the circuit comprises; common output stage circuitry for use in both modes, and a dual mode power supply circuit for supplying said output stage in the first mode with a lower supply voltage than in the second mode; and means for limiting the circuit'"'"'s output current when operating in said second mode, such that maximum power output in said second mode is less than that in the first mode, in spite of the higher maximum voltage amplitude.
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29. An audio amplifier circuit for providing an output signal to an audio transducer, said audio amplifier circuit comprising:
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a power amplifier having an audio input for receiving an audio input signal, an audio output for providing said output signal, and a pair of power supply rail connections substantially symmetric about a reference potential, forming a bi-polar power supply input; and a charge pump power supply for providing a bi-polar power supply voltage across said pair of power supply rail connections of said power amplifier, wherein said charge pump power supply has a select input for selecting an operating mode of said power supply, wherein in a first operating mode, said bi-polar power supply voltage is equal to a first voltage, and wherein in a second operating mode said -bi-polar power supply voltage is substantially equal to a rational fraction of said first voltage-, wherein in both of the first operating mode and the second operating mode, the bipolar power supply voltage is substantially symmetric about the reference potential wherein said charge pump power supply comprises first and second reservoir capacitors, each coupled between a respective one of said power supply rail connections and said reference potential and only a single flying capacitor. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37)
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Specification