This application relates to amplifier circuitry, in particular class-D amplifiers, operable in open-loop and closed-loop modes. An amplifier (300) has a forward signal path for receiving an input signal (S.sub.IN) and outputting an output signal (S.sub.OUT) and a feedback path operable to provide a feedback signal (S.sub.FB) from the output. A feedforward path provide a feedforward signal (S.sub.FF) from the input and a combiner (105) is operable to determine an error signal (ε) based on a difference between the feedback signal and the feedforward signal. The feedforward comprises a compensation module (201) configured to apply a controlled transfer function to the feedforward signal in the closed-loop mode of operation, such that an overall transfer function for the amplifier is substantially the same in the closed-loop mode of operation and the open-loop mode of operation.

This application relates to amplifier circuitry, in particular class-D amplifiers, operable in open-loop and closed-loop modes. An amplifier (300) has a forward signal path for receiving an input signal (S.sub.IN) and outputting an output signal (S.sub.OUT) and a feedback path operable to provide a feedback signal (S.sub.FB) from the output. A feedforward path provide a feedforward signal (S.sub.FF) from the input and a combiner (105) is operable to determine an error signal (ε) based on a difference between the feedback signal and the feedforward signal. The feedforward comprises a compensation module (201) configured to apply a controlled transfer function to the feedforward signal in the closed-loop mode of operation, such that an overall transfer function for the amplifier is substantially the same in the closed-loop mode of operation and the open-loop mode of operation.

Pulse width modulators 131P and 131N respectively generate a first pulse Vp whose pulse width changes according to an input signal Vin based on the input signal Vin and a generated first carrier wave C1P, and a second pulse Vn whose pulse width changes according to the input signal Vin based on the input signal Vin and a generated second carrier wave C1N. Wherein due to the non-liner gradient in each of the generated first carrier wave C1P and the generated second carrier wave C1N and, duty ratio of each of the generated first pulse Vp and the generated second pulse Vn is less than 50% in a state where a value of the input signal is zero; and a difference between a pulse width of the first pulse Vp and a pulse width of the second pulse Vn linearly changes according to the input signal Vin.

Pulse width modulators 131P and 131N respectively generate a first pulse Vp whose pulse width changes according to an input signal Vin based on the input signal Vin and a generated first carrier wave C1P, and a second pulse Vn whose pulse width changes according to the input signal Vin based on the input signal Vin and a generated second carrier wave C1N. Wherein due to the non-liner gradient in each of the generated first carrier wave C1P and the generated second carrier wave C1N and, duty ratio of each of the generated first pulse Vp and the generated second pulse Vn is less than 50% in a state where a value of the input signal is zero; and a difference between a pulse width of the first pulse Vp and a pulse width of the second pulse Vn linearly changes according to the input signal Vin.

A class-D amplifier includes: a gain control unit that amplifies an input audio signal in accordance with a compensation gain to generate an input signal Vin; and a pulse width modulator that generates a first pulse Vp whose pulse width changes according to the input signal Vin within a first input range A1 where a value of the generated input signal Vin is higher than a first boundary Vb1, and that generates a second pulse Vn whose pulse width changes according to the generated input signal Vin within a second input range A2. The gain control unit controls the compensation gain so that first inclination of an input/output characteristic of the class-D amplifier in a first section in which the pulse width modulator outputs both the first pulse Vp and the second pulse Vn and second inclination of the input/output characteristic in a second section other than the first section are similar to each other.

A class-D amplifier includes: a gain control unit that amplifies an input audio signal in accordance with a compensation gain to generate an input signal Vin; and a pulse width modulator that generates a first pulse Vp whose pulse width changes according to the input signal Vin within a first input range A1 where a value of the generated input signal Vin is higher than a first boundary Vb1, and that generates a second pulse Vn whose pulse width changes according to the generated input signal Vin within a second input range A2. The gain control unit controls the compensation gain so that first inclination of an input/output characteristic of the class-D amplifier in a first section in which the pulse width modulator outputs both the first pulse Vp and the second pulse Vn and second inclination of the input/output characteristic in a second section other than the first section are similar to each other.

In each E-class inverter, an internal voltage detection circuit detects an internal voltage of a resonant type power supply circuit or a matching circuit and adjusts a phase of a driving signal of a MOSFET based on a detected voltage. It is thus possible to match a phase of a current voltage of a sine waveform of each inverter and combine power highly efficiently. Since power combining is performed highly efficiently without using a variable capacitor and variable inductor, it is possible to suppress upsizing of elements and achieve downsizing of a power amplifier circuit.

A circuit includes an input impedance, an operational amplifier, a voltage-adjusting circuit, a pulse-generating circuit, and a drive circuit. The input impedance is coupled to an input terminal of the operational amplifier, receives an input voltage, and outputs an input current. The operational amplifier is coupled to a first power voltage and outputs an amplified signal according to an input operating voltage and a feedback signal. The voltage-adjusting circuit adjusts the input operating voltage of the operational amplifier. The pulse-generating circuit generates a pulse width modulation signal according to the amplified signal. The drive circuit is coupled to a second power voltage and generates a driving signal according to the pulse width modulation signal. The feedback signal is correlated with the driving signal.

A circuit includes an input impedance, an operational amplifier, a voltage-adjusting circuit, a pulse-generating circuit, and a drive circuit. The input impedance is coupled to an input terminal of the operational amplifier, receives an input voltage, and outputs an input current. The operational amplifier is coupled to a first power voltage and outputs an amplified signal according to an input operating voltage and a feedback signal. The voltage-adjusting circuit adjusts the input operating voltage of the operational amplifier. The pulse-generating circuit generates a pulse width modulation signal according to the amplified signal. The drive circuit is coupled to a second power voltage and generates a driving signal according to the pulse width modulation signal. The feedback signal is correlated with the driving signal.

A semiconductor device includes: a first buffer at which a predetermined signal is input and that outputs a first output signal; a second buffer at which an inverted signal of the predetermined signal is input and that outputs a second output signal; and a short circuit detection circuit that, in accordance with a potential difference between the first output signal and the second output signal, outputs a short circuit evaluation signal evaluating whether or not there is a ground fault in at least one of a first terminal at an output side of the first buffer or a second terminal at an output side of the second buffer or evaluating whether or not there is a short circuit between the first terminal and the second terminal.