An apparatus in a PWM modulator includes a triangular wave generator that generates a triangular wave and a comparator that is responsive to a signal input to generate a signal output. An output of the PWM modulator is responsive to the comparator signal output. A polarity inversion circuit, coupled between the triangular wave generator and the comparator, is configured in one of the following ways: to provide the triangular wave to the comparator when the triangular wave has a first slope polarity and to provide a polarity-inverted version of the triangular wave to the comparator when the triangular wave has a second slope polarity opposite the first slope polarity; and to provide the signal input to the comparator when the triangular wave has the first slope polarity and to provide a polarity-inverted version of the signal input to the comparator when the triangular wave has the second slope polarity.

An apparatus in a PWM modulator includes a triangular wave generator that generates a triangular wave and a comparator that is responsive to a signal input to generate a signal output. An output of the PWM modulator is responsive to the comparator signal output. A polarity inversion circuit, coupled between the triangular wave generator and the comparator, is configured in one of the following ways: to provide the triangular wave to the comparator when the triangular wave has a first slope polarity and to provide a polarity-inverted version of the triangular wave to the comparator when the triangular wave has a second slope polarity opposite the first slope polarity; and to provide the signal input to the comparator when the triangular wave has the first slope polarity and to provide a polarity-inverted version of the signal input to the comparator when the triangular wave has the second slope polarity.

A PWM modulator has a quantizer that generates a PWM output signal to speaker driver. When a first voltage swing range is supplied to the speaker driver, the quantizer analog gain is controlled to be a first gain value. When a second PWM drive voltage swing range is supplied to the speaker driver, the analog gain is controlled to be a second gain value. The first and second gain values of the analog gain of the quantizer cause the combined gain of the quantizer and driver to be approximately equal in the two modes. The quantizer has at least two gain-affecting measurable non-ideal characteristics. The quantizer is adjustable using measured first and second values to correct for first and second of the at least two non-ideal characteristics. The gain of the quantizer is calibratable while the quantizer is adjusted using the measured first and second measured values.

An apparatus in a PWM modulator includes a triangular wave generator that generates a triangular wave and a comparator that is responsive to a signal input to generate a signal output. An output of the PWM modulator is responsive to the comparator signal output. A polarity inversion circuit, coupled between the triangular wave generator and the comparator, is configured in one of the following ways: to provide the triangular wave to the comparator when the triangular wave has a first slope polarity and to provide a polarity-inverted version of the triangular wave to the comparator when the triangular wave has a second slope polarity opposite the first slope polarity; and to provide the signal input to the comparator when the triangular wave has the first slope polarity and to provide a polarity-inverted version of the signal input to the comparator when the triangular wave has the second slope polarity.

A digitally controlled oscillator (100), a synthesizer module (200), a synthesizer (300), and a method for producing an electrical audio signal are presented. The oscillator (100) comprises a digital processing unit (10) configured to generate a first pulse wave at a first output (PulseUp) of the processing unit (10), wherein the first pulse wave is arranged to include pulses at at least two different frequencies. The oscillator (100) further comprises a summing circuit (30) and a linear wave shaper (20). The output (PulseUp) of the processing unit (10) is connected to the summing circuit (30) which is arranged to produce a resultant signal based on at least the first pulse wave. The resultant signal is arranged to be fed into the linear wave shaper (20) which is arranged to produce an output signal at the output (OUT) of the oscillator (100) based on modifying the resultant signal.

A digitally controlled oscillator (100), a synthesizer module (200), a synthesizer (300), and a method for producing an electrical audio signal are presented. The oscillator (100) comprises a digital processing unit (10) configured to generate a first pulse wave at a first output (PulseUp) of the processing unit (10), wherein the first pulse wave is arranged to include pulses at at least two different frequencies. The oscillator (100) further comprises a summing circuit (30) and a linear wave shaper (20). The output (PulseUp) of the processing unit (10) is connected to the summing circuit (30) which is arranged to produce a resultant signal based on at least the first pulse wave. The resultant signal is arranged to be fed into the linear wave shaper (20) which is arranged to produce an output signal at the output (OUT) of the oscillator (100) based on modifying the resultant signal.

A signal output circuit includes a slope control circuit, a capacitor, a noise detector circuit and a fail-safe circuit. The slope control circuit charges and discharges the capacitor, the first terminal of which is connected to an output terminal, according to the control signal level, and drives transistors using the voltage of the second terminal of the capacitor, thereby controlling the slope of the output single. The noise detector circuit detects noise superimposed on the output terminal. When noise is detected, the fail-safe circuit performs a forced drive operation on the transistor to output the output signal at a level corresponding to the level of the control signal is output, regardless of the transistor being driven by the slope control circuit.

A signal output circuit includes a slope control circuit, a capacitor, a noise detector circuit and a fail-safe circuit. The slope control circuit charges and discharges the capacitor, the first terminal of which is connected to an output terminal, according to the control signal level, and drives transistors using the voltage of the second terminal of the capacitor, thereby controlling the slope of the output single. The noise detector circuit detects noise superimposed on the output terminal. When noise is detected, the fail-safe circuit performs a forced drive operation on the transistor to output the output signal at a level corresponding to the level of the control signal is output, regardless of the transistor being driven by the slope control circuit.

A signal output circuit includes a slope control circuit, a capacitor, a noise detector circuit and a fail-safe circuit. The slope control circuit charges and discharges the capacitor, the first terminal of which is connected to an output terminal, according to the control signal level, and drives transistors using the voltage of the second terminal of the capacitor, thereby controlling the slope of the output single. The noise detector circuit detects noise superimposed on the output terminal. When noise is detected, the fail-safe circuit performs a forced drive operation on the transistor to output the output signal at a level corresponding to the level of the control signal is output, regardless of the transistor being driven by the slope control circuit.

A signal output circuit includes a slope control circuit, a capacitor, a noise detector circuit and a fail-safe circuit. The slope control circuit charges and discharges the capacitor, the first terminal of which is connected to an output terminal, according to the control signal level, and drives transistors using the voltage of the second terminal of the capacitor, thereby controlling the slope of the output single. The noise detector circuit detects noise superimposed on the output terminal. When noise is detected, the fail-safe circuit performs a forced drive operation on the transistor to output the output signal at a level corresponding to the level of the control signal is output, regardless of the transistor being driven by the slope control circuit.