Apparatus (301) for switchable attenuation of a differential input signal from a microphone includes positive and negative non-attenuating paths (406, 410) have n- and p-type MOSFETs (421, 422, 423, 424) in back-to-back configurations; positive and negative attenuating paths (405, 409) have n- and p-type MOSFETs (415, 416, 418, 419) in back-to-back configurations in combination with resistors; a gate driver (425) applies a drive signal of one polarity (QNEG) to gates of the n-type MOSFETs in the attenuating paths and the p-type MOSFETs in the non-attenuating paths, and a drive signal of opposite polarity (QPOS) to the gates of the p-type MOSFETs in the attenuating paths and the n-type MOSFETs in the non-attenuating paths; and the state of the MOSFETs depends on the drive signals at their gates, and thus the input signal may be routed via either the non-attenuating paths or the attenuating paths by controlling the drive signals.

Methods and apparatus are provided to improve the efficiency of an outphasing amplifier through modulating the phase angle of a reflected signal in the outphasing amplifier. An outphasing amplifier includes a first amplifier and a second amplifier. A circulator is provided having a first port coupled to an output of the outphasing amplifier, a second port coupled to a load and a third port coupled to a phase shifter. The phase shifter is configured to provide a different phase angle of a reflected signal from the phase shifter to the outphasing amplifier through the circulator.

An active device and circuits utilized therewith are disclosed. In an aspect, the active device comprises an n-type transistor having a drain, gate and bulk and a p-type transistor having a drain, gate and bulk. The n-type transistor and the p-type transistor include a common source. The device includes a first capacitor coupled between the gate of the n-type transistor and the gate of the p-type transistor, a second capacitor coupled between the drain of the n-type transistor and the drain of p-type transistor and a third capacitor coupled between the bulk of the n-type transistor and the bulk of p-type transistor. The active device has a high breakdown voltage, is memory less and traps even harmonic signals.

A variable-gain power amplifying technique includes generating, with a network of one or more reactive components included in an oscillator, a first oscillating signal, and outputting, via one or more taps included in the network of the reactive components, a second oscillating signal. The second oscillating signal has a magnitude that is proportional to and less than the first oscillating signal. The power amplifying technique further includes selecting one of the first and second oscillating signals to use for generating a power-amplified output signal, and amplifying the selected one of the first and second oscillating signals to generate the power-amplified output signal.

The present invention provides a transducer protection system and method. A transducer module at least comprises a transducer, and a signal source is used for generating a first signal; a protection module is used for predicting an actual displacement and/or temperature of the transducer according to the first signal, an amplification factor of the power amplifier and built-in transducer parameters to generate a prediction result, comparing the prediction result with a preset value to generate an analysis result, and regulating the first signal to form a second signal according to the analysis result; a power amplifier is used for receiving the second signal, and performing power amplification on the second signal to form a driving signal; and the transducer module is used for receiving the driving signal, and at least one transducer in the transducer module can work according to the driving signal.