Embodiments of the present disclosure provide a chopper amplifier circuit that includes an operational amplifier, and a notch filter to be operated by a chopping pulse. The notch filter has a first branch that has a first capacitor, and a second branch that has a second capacitor. A chopping delay switch is connected to the first branch and the second branch of the notch filter. A control circuit is to close the chopping delay switch to short-circuit the first branch and the second branch of the notch filter to each other. The control circuit is to detect establishment of feedback signal at the chopper amplifier. The control circuit is to open the chopping delay switch, responsive to detecting establishment of the feedback signal at the chopper amplifier.

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 compact directed energy system is disclosed that is configured to generate directed energy beams. The compact directed energy system includes a radio frequency system configured to provide a directed energy beam in a frequency range between 500 MHz to 20 Ghz.

A power amplifier apparatus includes a semiconductor substrate, a plurality of first transistors on the semiconductor substrate, a plurality of second transistors, at least one collector terminal electrically connected to collectors of the plurality of first transistors, a first inductor having a first end electrically connected to the collector terminal and a second end electrically connected to a power supply potential, at least one emitter terminal electrically connected to emitters of the plurality of second transistors and adjacent to the collector terminal in a second direction, a second inductor having a first end electrically connected to the emitter terminal and a second end electrically connected to a reference potential, and at least one capacitor having a first end electrically connected to the collectors of the plurality of first transistors and a second end electrically connected to the emitters of the plurality of second transistors.

An output switch includes; a plurality of input terminals and output terminals each of the plurality of input terminals is electrically connected to at least one of the plurality of output terminals; a first low noise amplifier that amplifies a signal of a predetermined frequency band input through an antenna and outputs a first signal to a first input terminal among the plurality of input terminals, and a second low noise amplifier that amplifies a signal of a predetermined frequency band input through an antenna and outputs a second signal to a second input terminal different from the first input terminal among the plurality of input terminals. A filter that attenuates a signal of a frequency band higher than a frequency band of the second signal is electrically connected between the second input terminal and the second low noise amplifier.

Apparatus and methods for power amplifier bias modulation for low bandwidth envelope tracking are provided herein. In certain embodiments, a power amplifier system for a mobile device 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.

A programmable analog beamformer controls phase and amplitude of radio frequency sine signals independently on n channels. In a preferred embodiment, each of n channels achieves full cycle phase sifting by using m first order programmable filters isolated by buffer amplifiers, with maximum phase shift amount of 180/m degrees in each filter. By flipping the polarity of sine signal in differential path, the beamformer achieves additional 180 degrees phase shift. There is an amplitude control unit in each channel, that both compensates amplitude attenuations due to phase shifting of filters, and to control the amplitude of the RF signal per user choice. There is a core algorithm software that handles all the digital programming of the system, as well as error correction of the phase and amplitude. The analog beamformer can drive piezoelectric ultrasonic transducers with no unwanted harmonics, or other loads per application.

A low noise amplifier (LNA) includes a first transistor and a second transistor. A source of the second transistor is connected to a drain of the first transistor. The LNA further includes a feedback transformer. A gate of the first transistor is connected to a primary winding of the feedback transformer and a gate of the second transistor is connected to a secondary winding of the feedback transformer.

A sensor device of the present invention includes first sensors receiving a plurality of driving signals; second sensors outputting a plurality of sensing signals in response to the driving signals; and a sensor receiver connected receiving the sensing signals from the second sensors, and including a band pass filter filtering the sensing signals. The band pass filter includes a multi-path filter in which a frequency of the driving signals is set as a center frequency; a gain amplifier amplifying signals filtered through the multi-path filter according to a predetermined gain value; and a buffer isolating the multi-path filter and the gain amplifier from each other.

A Class D amplifier having an integrating primary amplifier with an internal feedback, the amplifier further comprising a feedback loop with a filter of at least second order.