A direct current (DC) offset protection circuit includes: a DC offset detection circuit and a control circuit. The DC offset detection circuit is arranged to detect whether a DC component exists in pulse-width-modulation (PWM) signals and accordingly generate a DC offset detection result. The control circuit is arranged to control an audio system according to the DC offset detection result. The DC offset detection circuit comprises a PWM polarity judgment circuit, a cascaded integrator-comb (CIC) filter and a DC offset judgment circuit. The PWM polarity judgment circuit is arranged to judge a polarity of complementary PWM signals and accordingly generate a polarity indication value. The CIC filter is arranged to generate a filter output signal by averaging a plurality of polarity indication values. The DC offset judgment circuit is arranged to generate the DC offset detection result by comparing the filter output signal with a predetermined DC threshold.

A direct current (DC) offset protection circuit includes: a DC offset detection circuit and a control circuit. The DC offset detection circuit is arranged to detect whether a DC component exists in pulse-width-modulation (PWM) signals and accordingly generate a DC offset detection result. The control circuit is arranged to control an audio system according to the DC offset detection result. The DC offset detection circuit comprises a PWM polarity judgment circuit, a cascaded integrator-comb (CIC) filter and a DC offset judgment circuit. The PWM polarity judgment circuit is arranged to judge a polarity of complementary PWM signals and accordingly generate a polarity indication value. The CIC filter is arranged to generate a filter output signal by averaging a plurality of polarity indication values. The DC offset judgment circuit is arranged to generate the DC offset detection result by comparing the filter output signal with a predetermined DC threshold.

Systems and methods are provided for amplifying multiple input signals to generate multiple output signals. An example system includes a first channel, a second channel, and a third channel. The first channel is configured to receive one or more first input signals, process information associated with the one or more first input signals and a first ramp signal, and generate one or more first output signals. The second channel is configured to receive one or more second input signals, process information associated with the one or more second input signals and a second ramp signal, and generate one or more second output signals. The first ramp signal corresponds to a first phase. The second ramp signal corresponds to a second phase. The first phase and the second phase are different.

Systems and methods are provided for amplifying multiple input signals to generate multiple output signals. An example system includes a first channel, a second channel, and a third channel. The first channel is configured to receive one or more first input signals, process information associated with the one or more first input signals and a first ramp signal, and generate one or more first output signals. The second channel is configured to receive one or more second input signals, process information associated with the one or more second input signals and a second ramp signal, and generate one or more second output signals. The first ramp signal corresponds to a first phase. The second ramp signal corresponds to a second phase. The first phase and the second phase are different.

A method for matching a pair of composite circuit elements (CEs) included in a circuit includes fabricating N CEs (e.g., resistors, transistors, current sources, capacitors) designed to match and switches configurable, according to M different combinations, to connect N/2 of the N CEs to form a first composite CE and to connect a remaining N/2 of the N CEs to form a second composite CE. Sequentially in time, for each combination of the M combinations, the switches are configured to form the first and second composite CEs according to the combination and a characteristic of the circuit is measured that includes the formed first and second composite CEs. The characteristic indicates how well the formed composite CEs match. A final combination of the M combinations is chosen whose measured characteristic indicates a best match and the final combination is used to configure the switches to form the composite CEs.

A power amplifier that includes a substrate, and an emitter layer, a base layer, and a collector layer laminated in this order on a major surface of the substrate includes an electrical insulator provided adjacent to the emitter layer, an emitter electrode provided between the substrate and both the emitter layer and the electrical insulator, a base electrode electrically connected to the base layer, and a collector electrode electrically connected to the collector layer. The emitter electrode, the electrical insulator, and the base layer are provided between the substrate and the base electrode in a direction perpendicular to the major surface of the substrate.

A power amplifier that includes a substrate, and an emitter layer, a base layer, and a collector layer laminated in this order on a major surface of the substrate includes an electrical insulator provided adjacent to the emitter layer, an emitter electrode provided between the substrate and both the emitter layer and the electrical insulator, a base electrode electrically connected to the base layer, and a collector electrode electrically connected to the collector layer. The emitter electrode, the electrical insulator, and the base layer are provided between the substrate and the base electrode in a direction perpendicular to the major surface of the substrate.

A control circuit and a method for controlling a piezoelectric transformer are disclosed. In an embodiment the control circuit includes an inductor and a control unit, wherein the control circuit is configured to apply a voltage with a periodic waveform to a piezoelectric transformer, wherein a period duration of the voltage is specified by a control frequency and adjust the control frequency of the applied voltage as a function of an average current intensity of a current flowing through the inductor.

A power supply for supplying a power to a heating mechanism used for heating a measurement target that emits a measurement signal includes an input device configured to output an input signal that reflects a control signal in a differentiable periodic waveform having a frequency of 1 kHz or less. The power supply includes a switching amplifier configured to amplify the input signal from the input device and output the amplified signal.

A power supply for supplying a power to a heating mechanism used for heating a measurement target that emits a measurement signal includes an input device configured to output an input signal that reflects a control signal in a differentiable periodic waveform having a frequency of 1 kHz or less. The power supply includes a switching amplifier configured to amplify the input signal from the input device and output the amplified signal.