Switching amplifier
First Claim
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1. A pulse-width modulation circuit, comprising:
- a comparator whose output swings between first and second voltage levels in accordance with the polarity of the voltage difference between the comparator'"'"'s non-inverting and inverting inputs;
wherein the comparator'"'"'s inverting input is connected to the comparator output through a feedback resistor, to ground through a capacitor, and to an input signal through an input resistor;
wherein the comparator'"'"'s non-inverting input is maintained at a constant potential;
means for providing a sufficient propagation delay in a path comprising the comparator and feedback resistor so that the capacitor charges for some time after a change in the polarity of the voltage difference between the comparator'"'"'s inverting and non-inverting inputs, the capacitor voltage being substantially a triangular waveform which thereby causes the comparator output to be a square wave at a frequency determined by the values of the capacitor, feedback resistor, and first and second voltage levels;
and, wherein an input signal applied to the comparator'"'"'s inverting input causes the comparator output to be pulse width modulated by the input signal.
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Abstract
An improved digital switching amplifier is disclosed. The amplifier utilizes a low-pass filter at the input of the switching comparator to give an improved signal to noise ratio at the final output. In another aspect of the invention, a propagation delay is used to produce the steady-state oscillation of the amplifier circuit.
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Citations
13 Claims
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1. A pulse-width modulation circuit, comprising:
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a comparator whose output swings between first and second voltage levels in accordance with the polarity of the voltage difference between the comparator'"'"'s non-inverting and inverting inputs; wherein the comparator'"'"'s inverting input is connected to the comparator output through a feedback resistor, to ground through a capacitor, and to an input signal through an input resistor; wherein the comparator'"'"'s non-inverting input is maintained at a constant potential; means for providing a sufficient propagation delay in a path comprising the comparator and feedback resistor so that the capacitor charges for some time after a change in the polarity of the voltage difference between the comparator'"'"'s inverting and non-inverting inputs, the capacitor voltage being substantially a triangular waveform which thereby causes the comparator output to be a square wave at a frequency determined by the values of the capacitor, feedback resistor, and first and second voltage levels; and, wherein an input signal applied to the comparator'"'"'s inverting input causes the comparator output to be pulse width modulated by the input signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 11, 12, 13)
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9. A switching amplifier, comprising:
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a comparator with inverting and non-inverting inputs having its output connected to its inverting input through a feedback resistor and its inverting input connected to an input signal through an input resistor; a capacitor connecting the inverting input of the comparator to ground; a comparator whose output swings between first and second voltage levels in accordance with the polarity of the voltage difference between the comparator'"'"'s non-inverting and inverting inputs; wherein the comparator'"'"'s inverting input is connected to the comparator output through a feedback resistor, to ground through a capacitor, and to an input signal through an input resistor; a first resistor connecting the comparator non-inverting input to ground; a second resistor connecting the comparator output to the comparator non-inverting input, the first and second resistors thereby forming a voltage divider for feeding back a portion of the comparator'"'"'s output to its non-inverting input so that after a change in the comparator output the capacitor charges up to the voltage across the first resistor before the comparator output changes, the capacitor voltage thereby being substantially a triangular waveform; a first low pass filter for recovering the input signal from the comparator output; and a second low pass filter between the capacitor and the inverting input of the comparator for converting the triangular capacitor voltage waveform into a substantially sinusoidal waveform in order to improve the signal to noise ratio of the amplifier. - View Dependent Claims (10)
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Specification