PWM loop filter with minimum aliasing error
First Claim
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1. An audio amplifier comprising:
- a loop filter having a transfer function with a real part being minimized at and above a switching frequency of the audio amplifier, wherein the loop filter has a dominant pole placed substantially at or above an upper frequency in a range of input frequencies processed by the audio amplifier;
an adder having;
a first resistor that receives a clock signal and that is coupled to the loop filter;
a second resistor that receives the input signal and that is coupled to the loop filter; and
a third resistor that is receives the feedback signal and that is coupled to the loop filter; and
an output stage that is coupled to the adder.
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Abstract
One embodiment of an apparatus for filtering an electrical signal includes a loop filter with an input and an output that applies a transfer function to a signal at the input. The transfer function has substantially no real part. The loop filter has a dominant pole placed substantially at or above an upper frequency in the frequency range of interest for the loop filter.
30 Citations
11 Claims
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1. An audio amplifier comprising:
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a loop filter having a transfer function with a real part being minimized at and above a switching frequency of the audio amplifier, wherein the loop filter has a dominant pole placed substantially at or above an upper frequency in a range of input frequencies processed by the audio amplifier; an adder having; a first resistor that receives a clock signal and that is coupled to the loop filter; a second resistor that receives the input signal and that is coupled to the loop filter; and a third resistor that is receives the feedback signal and that is coupled to the loop filter; and an output stage that is coupled to the adder.
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2. An audio amplifier comprising:
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a loop filter having a transfer function with a real part being minimized at and above a switching frequency of the audio amplifier, wherein the loop filter has a dominant pole placed substantially at or above an upper frequency in a range of input frequencies processed by the audio amplifier; an adder that receives a feedback signal and that is coupled to the loop filter, wherein at least one of the loop filter and the adder receives an input signal; and an output stage having; a comparator that is coupled to at least one of the loop filter and the adder; and a switching power stage that is coupled to the comparator. - View Dependent Claims (3, 4, 5)
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6. An audio amplifier comprising:
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a loop filter having a transfer function with a real part being minimized at and above a switching frequency of the audio amplifier, wherein the loop filter has a dominant pole placed substantially at or above an upper frequency in a range of input frequencies processed by the audio amplifier, and wherein the loop filter includes; a first resistor; a first leg having a second resistor and a first capacitor coupled in series with one another; a third resistor; and a second leg having a second capacitor, wherein the first resistor, the first leg, the third resistor, and the second leg are coupled in series with one another; an adder that receives a feedback signal and that is coupled to the loop filter, wherein at least one of the loop filter and the adder receives an input signal; and an output stage that is coupled to the adder. - View Dependent Claims (7, 8, 9, 10, 11)
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Specification