Switching amplifier

Claim 2

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.

Claim 3

The modulation circuit as set forth in claim 1 further comprising a 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.

Claim 4

The modulation circuit as set forth in claim 2 wherein the low pass filter comprises a resistor and capacitor connected between the comparator inverting input and ground.

Claim 5

The modulation circuit as set forth in claim 1 wherein the propagation delay means comprises an all-pass filter network.

Claim 6

The modulation circuit as set forth in claim 1 further comprising a first low pass filter at the output of the comparator for recovering the input signal from the pulse width modulated comparator output signal, the circuit thereby becoming a switching amplifier.

Claim 7

The circuit as set forth in claim 5 further comprising 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.

Claim 8

The circuit as set forth in claim 5 wherein the propagation delay means comprises an all-pass filter network.

Claim 9

The circuit as set forth in claim 5 wherein the propagation delay means comprises an additional amplifier stage between the comparator output and the feedback resistor.

Claim 10

A switching amplifier, comprising: 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.

Claim 11

A switching amplifier, comprising: 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.

Claim 12

The amplifier as set forth in claim 9 wherein the second low pass filter comprises a resistor and capacitor connecting the inverting input of the comparator to ground.

Claim 13

The circuit as set forth in claim 6 wherein the second low pass filter comprises a resistor and capacitor connected between the comparator inverting input and ground.

Claim 14

The circuit as set forth in claim 6 wherein the propagation delay means comprises an all-pass filter network.

Claim 15

The circuit as set forth in claim 6 wherein the propagation delay means comprises an additional amplifier stage between the comparator output and the feedback resistor.