Techniques for reducing electromagnetic interference (EMI) in a switching amplifier circuit, control edge-rate with reduced sensitivity to process and temperature variations and that is reduced with increasing power supply voltage. The techniques control current levels in a pre-driver stage that drives an output driver of a switching amplifier circuit, according to a bias control. A first slope of a variation of the bias control with respect to a power supply voltage of the switching amplifier circuit over a first portion of a range of variation of the power supply voltage has a direction opposite a second slope of the variation of the reference output current with respect to the power supply voltage over a second portion of the range of variation of the power supply voltage. The resulting operation reduces electromagnetic interference generated by the driver over the second portion of the range of variation of the power supply voltage.

A semiconductor device includes a semiconductor chip that has a main surface, a device region that is demarcated at the main surface, a differential amplifier that is formed in the device region and that amplifies and outputs a differential signal input to the differential amplifier, an insulation layer that covers the device region on the main surface, and a shield electrode that is incorporated in the insulation layer such as to conceal the device region in a plan view and that is fixed to a ground potential.

The present invention is a Class-D amplifier including: a capacitively-coupled amplifier, configured to receive an input signal and a feedback signal and generate an error signal; and a loop filter, coupled to input capacitor and the feedback capacitor, configured to generate a processed signal according to the error signal; and a pulse-width modulation (PWM) generator, coupled to the loop filter, configured to generate a plurality of PWM signals according to the processed signal and a control signal; and a voltage boosting power stage, coupled to the PWM generator, configured to generate a boosted output signal according to the plurality of PWM signals, the control signal and a power supply, and to feedback the boosted output signal to the loop filter, wherein the maximum voltage of the boosted output signal is greater than the voltage of the power supply.

An output matching circuit includes a transformer having one end electrically connected to an output terminal of a power amplifier element that amplifies an input signal and another end electrically connected to a terminal connected to a load, and converting an impedance of the terminal connected to the load to an impedance higher than an impedance of the output terminal, a first filter circuit that attenuates a signal within a first frequency band higher than a transmission frequency band of the input signal, and a second filter circuit that attenuates a signal within a second frequency band higher than the first frequency band.