Patent ID: 6956431

Claim:
A pulse width modulation amplifier comprising: an input terminal that receives a signal; a triangular wave-generating device that generates a triangular wave; a pulse width modulation amplification device that performs pulse width modulation amplification of the signal input via said input terminal based on the triangular wave generated by said triangular wave-generating device; and an output terminal that outputs the signal subjected to the pulse width modulation amplification by said pulse width modulation amplification device, wherein said triangular wave-generating device comprises an integrating device that includes an amplifier having a signal input terminal and a signal output terminal, and a capacitance element connected between said signal input terminal and said signal output terminal of said amplifier, a first constant-current device that charges said capacitance element such that an output voltage from said amplifier becomes equal to a first predetermined voltage, by causing a constant current to flow through said capacitance element in a predetermined direction, a second constant-current device that discharges said capacitance element such that the output voltage from said amplifier becomes equal to a second predetermined voltage lower than the first predetermined voltage, by causing a constant current to flow through said capacitance element in a direction opposite to the predetermined direction, a constant-current value-setting device that sets values of the constant currents caused to flow by said first and second constant-current devices, a changing device that changes the values of the constant currents set by said constant-current value-setting device, a first switching device that turns on or off to allow or block flowing of the constant current caused to flow by said first constant-current device, a second switching device that turns on or off to allow or block flowing of the constant current caused to flow by said second constant-current device, a first comparison device that compares the output voltage from said amplifier and the first predetermined voltage for outputting a signal of a logic level dependent on a result of the comparison, a second comparison device that compares the output voltage from said amplifier and the second predetermined voltage for outputting a signal of a logic level dependent on a result of the comparison, and a flip-flop that inverts a logic level of an output signal therefrom when it is detected by said first comparison device that the output voltage from said amplifier has increased to reach the first predetermined voltage, or when it is detected by said second comparison device that the output voltage from said amplifier has decreased to reach the second predetermined voltage, whereby said first and second switching devices turn on or off, depending the logic level of the output signal from said flip-flop.