Class-D amplifier with post filter feedback loop
First Claim
1. A class-D amplifier, comprising:
- an L-C filter;
an output driver, wherein an output terminal of the output driver is coupled to an input terminal of the L-C filter;
a second order filter; and
a summing amplifier;
wherein;
a first input terminal of the summing amplifier is coupled to an output terminal of the L-C filter; and
a second input terminal of the summing amplifier is coupled to a first output terminal of the second order filter;
further comprising a differentiator, wherein a third input terminal of the summing amplifier is coupled to the output terminal of the L-C filter via the differentiator.
1 Assignment
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Accused Products
Abstract
A fixed frequency class-D audio amplifier includes the L-C output filter in a high order feedback loop. An audio amplifier integrated circuit includes an output driver, an output terminal, a first input terminal, a second order filter, and a summing amplifier. The output driver is configured to drive a speaker coil through an L-C filter. The output terminal is to couple the output driver to an input side of the L-C filter. The first input terminal is to couple an output side of the L-C filter to the integrated circuit. The second order filter includes a first filter stage, and a second filter stage coupled to an output of the first filter stage. The summing amplifier includes a first input coupled to the first input terminal, and a second input coupled to an output of the second filter stage.
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Citations
18 Claims
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1. A class-D amplifier, comprising:
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an L-C filter; an output driver, wherein an output terminal of the output driver is coupled to an input terminal of the L-C filter; a second order filter; and a summing amplifier; wherein; a first input terminal of the summing amplifier is coupled to an output terminal of the L-C filter; and a second input terminal of the summing amplifier is coupled to a first output terminal of the second order filter; further comprising a differentiator, wherein a third input terminal of the summing amplifier is coupled to the output terminal of the L-C filter via the differentiator.
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2. A class-D amplifier, comprising:
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an L-C filter; an output driver, wherein an output terminal of the output driver is coupled to an input terminal of the L-C filter; a second order filter; and a summing amplifier; wherein; a first input terminal of the summing amplifier is coupled to an output terminal of the L-C filter; and a second input terminal of the summing amplifier is coupled to a first output terminal of the second order filter; wherein a third input terminal of the summing amplifier is coupled to a second output terminal of the second order filter. - View Dependent Claims (3)
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4. A class-D amplifier, comprising:
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an L-C filter; an output driver, wherein an output terminal of the output driver is coupled to an input terminal of the L-C filter; a second order filter; and a summing amplifier; wherein; a first input terminal of the summing amplifier is coupled to an output terminal of the L-C filter; and a second input terminal of the summing amplifier is coupled to a first output terminal of the second order filter; wherein a first input terminal of the second order filter is coupled to the output terminal of the L-C filter.
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5. A class-D amplifier, comprising:
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an L-C filter; an output driver, wherein an output terminal of the output driver is coupled to an input terminal of the L-C filter; a second order filter; and a summing amplifier; wherein; a first input terminal of the summing amplifier is coupled to an output terminal of the L-C filter; and a second input terminal of the summing amplifier is coupled to a first output terminal of the second order filter; further comprising a signal input terminal coupled to a first input terminal of the second order filter and a third input terminal of the summing amplifier.
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6. A class-D amplifier, comprising:
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an L-C filter; an output driver, wherein an output terminal of the output driver is coupled to an input terminal of the L-C filter; a second order filter; and a summing amplifier; wherein; a first input terminal of the summing amplifier is coupled to an output terminal of the L-C filter; and a second input terminal of the summing amplifier is coupled to a first output terminal of the second order filter; wherein the L-C filter, the second order filter and the summing amplifier are connected to form a loop filter that provides at least 60 decibels of gain over a frequency range of 20 Hertz to 20 kilo-Hertz.
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7. An audio amplifier integrated circuit, comprising:
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an output driver configured to drive a speaker coil through an L-C filter; an output terminal to couple the output driver to an input side of the L-C filter; and a first input terminal to couple an output side of the L-C filter to the integrated circuit; a second order filter comprising; a first filter stage; and a second filter stage coupled to an output of the first filter stage; and a summing amplifier comprising; a first input coupled to the first input terminal; a second input coupled to an output of the second filter stage. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. An integrated circuit, comprising:
a class-D audio amplifier, comprising; an output driver configured to drive a speaker coil through an L-C filter; an output terminal to couple the output driver to an input side of the L-C filter; and a first input terminal to couple an output side of the L-C filter to the integrated circuit; a second order filter comprising; a first filter stage coupled to the first input terminal; and a second filter stage coupled to an output of the first filter stage; a summing amplifier comprising; a first input coupled to the first input terminal; a second input coupled to an output of the second filter stage; and a differentiator coupled to the first input terminal and to a third input of the summing amplifier. - View Dependent Claims (15, 16, 17, 18)
Specification