An electromyography (EMG) device according to an aspect of the present disclosure includes a main circuit board having opposing first and second faces. A plurality of first connectors of a first type are provided on the first face, and a plurality of input contacts are provided on the second face. An EMG circuit is provided on the main circuit board. The EMG circuit is configured to utilize the input contacts as inputs to obtain an EMG input signal, and process the EMG input signal to provide an EMG output signal that is based on, but different from, the EMG input signal. For each of the input contacts, there is no conductive path directly between the input contact and any of the first connectors.

A high-frequency module (1) includes a first substrate (101), a second substrate (102) that faces the first substrate (101), a support (103) that supports the first substrate (101) and the second substrate (102), and a plurality of high-frequency circuit components arranged in internal space formed by the first substrate (101), the second substrate (102), and the support and on both of facing principal faces of the first substrate (101) and the second substrate (102), and the plurality of high-frequency circuit components include a power amplifier element that constitutes a power amplifier circuit (16).

An architecture of radio frequency front-end includes a power amplifier module integrated duplexer (PAMiD), an antenna and at least one tunable matching network; herein, the PAMiD includes a power amplifier, and the at least one tunable matching network is located between the power amplifier and the antenna, and is configured to adjust the impedance of the output end of the power amplifier and/or the impedance of the input end of the antenna.

A chopper-stabilized current feedback amplifier includes an input buffer having a non-inverting input and an inverting input. A first group of chopper circuits modulate current at the non-inverting and inverting inputs. The current feedback amplifier further includes a plurality of current mirrors coupled to the input buffer. A second group of chopper circuits modulate current in the current mirrors. The current feedback amplifier also includes phase detector circuitry coupled to the current mirrors and configured to detect a transition current in the current mirrors. The current feedback amplifier also includes a switched capacitor filter having an input coupled to the current mirrors. The switched capacitor filter is turned OFF responsive to the detection of the transition current by the phase detector circuitry. The current feedback amplifier also includes an output stage having an input coupled to the switched capacitor filter and is configured to produce an output signal.

Apparatus and methods for power amplifier bias modulation for multi-level supply envelope tracking are provided herein. In certain embodiments, an envelope tracking system includes a power amplifier that amplifies a radio frequency signal, a multi-level supply envelope tracker that generates a power amplifier supply voltage of the power amplifier based on an envelope signal indicating an envelope of the radio frequency signal, and a bias modulation circuit that modulates a bias of the power amplifier based on a voltage level of the power amplifier supply voltage.

Apparatus and methods for power amplifier bias modulation for low bandwidth envelope tracking are provided herein. In certain embodiments, an envelope tracking system includes a power amplifier that amplifies an RF signal and a low bandwidth envelope tracker that generates a power amplifier supply voltage for the power amplifier based on an envelope of the RF signal. The envelope tracking system further includes a bias modulation circuit that modulates a bias signal of the power amplifier based on a voltage level of the power amplifier supply voltage.

Multi-level envelope trackers with an analog interface are provided herein. In certain embodiments, an envelope tracking system for generating a power amplifier supply voltage for a power amplifier is provided. The envelope tracking system includes a multi-level supply (MLS) DC-to-DC converter that outputs multiple regulated voltages, an MLS modulator that controls selection of the regulated voltages over time based on an analog envelope signal corresponding to an envelope of the RF signal amplified by the power amplifier, and a modulator output filter coupled between an output of the MLS modulator and the power amplifier supply voltage.

Multi-level envelope tracking systems with separate DC and AC paths are provided. In certain embodiments, an envelope tracking system for generating a power amplifier supply voltage for a power amplifier is provided. The envelope tracking system includes a multi-level supply (MLS) DC-to-DC converter that outputs multiple regulated voltages, an MLS modulator that controls selection of the regulated voltages over time based on an envelope signal corresponding to an envelope of a radio frequency (RF) signal amplified by the power amplifier, an AC path filter coupled between an output of the MLS modulator and the power amplifier supply voltage, and a DC path filter coupled between a DC voltage and the power amplifier supply voltage.

The present disclosure provides an inductive magnetic sensor, which includes a signal pre-amplifying measurement circuit, a feedback loop, a magnetic core and coil group, a low-noise autozero processing circuit, and an output protection module. The magnetic core and coil group is electrically connected between the signal pre-amplifying measurement circuit and the feedback loop, the signal pre-amplifying measurement circuit comprises the low-noise autozero processing circuit, and the feedback loop and the low-noise autozero processing circuit are electrically connected to the output protection module respectively. By introducing the resonant notch filter, it may extend the passband to the low frequency, and extend the low-frequency characteristic of the magnetic sensor, to obtain a better low-frequency magnetic sensor. The present disclosure further provides an electromagnetic prospecting equipment.

A chopper amplifier circuit includes a first amplifier path, a second amplifier path, and a third amplifier path. The first amplifier path includes chopper circuitry configured to modulate an input signal and an offset voltage at a chopping frequency, and ripple reduction circuitry configured to attenuate the chopping frequency in a signal in the first amplifier path. The second amplifier path includes a feedforward gain stage, and is configured to apply higher gain to intermediate signal frequencies than is applied in the first amplifier path. The third amplifier path includes a feedforward gain stage, and is configured to apply higher gain to high signal frequencies than is applied in the first amplifier path and the second amplifier path. The intermediate signal frequencies are lower than the high signal frequencies.