A front-end amplifier circuit for receiving a biological signal includes a signal channel. The signal channel amplifies the biological signal to generate a detection current and includes a capacitive-coupled transconductance amplifier. The capacitive-coupled transconductance amplifier amplifies the biological signal with a transconductance gain to generate a first current.

An output signal can be free of any noise component generated from an amplifier disposed in a path, without degradation of the S/N ratio of the output signal. An amplifier includes: a first amplifier that is connected to an input node and generates a first intermediate signal; a feedback resistor that enables feedback of the first intermediate signal to the input node; an attenuator that receives the first intermediate signal and generates a second intermediate signal; a second amplifier that is connected to the input node and generates a third intermediate signal; a third amplifier that is connected to the input node and generates a fourth intermediate signal; and an adder that generates an output signal, using the second intermediate signal, the third intermediate signal, and the fourth intermediate signal.

Apparatus and methods for envelope tracking systems with automatic mode selection are provided herein. In certain configurations, a power amplifier system includes a power amplifier that amplifies a radio frequency signal and that receives power from a power amplifier supply voltage. The power amplifier system further includes an envelope tracker that generates the power amplifier supply voltage based on an envelope signal corresponding to an envelope of the radio frequency signal. The envelope tracker includes a signal bandwidth detection circuit that processes the envelope signal to generate a detected bandwidth signal, and a mode control circuit that controls a mode of the error amplifier based on the detected signal bandwidth.

An apparatus and method are provided for controlling the gain of a common source differential amplifier. The common source differential amplifier includes a pair of a metal-oxide-semiconductor field effect transistors (MOSFETs) each including a gate, a drain, and a source and at least one common source degeneration MOSFET in electrical communication between the sources of the pair of MOSFETs, the at least one common source degeneration MOSFET including a plurality of gate structures. A controller is in electrical communication with the gate structures and is configured to selectively activate one or more of the gate structures for controlling the gain of the common source differential amplifier.

In some embodiments, a method for processing an audio signal in an audio processing apparatus is disclosed. The method includes receiving an audio signal and a parameter, the parameter indicating a location of an auditory event boundary. An audio portion between consecutive auditory event boundaries constitutes an auditory event. The method further includes applying a modification to the audio signal based in part on an occurrence of the auditory event. The parameter may be generated by monitoring a characteristic of the audio signal and identifying a change in the characteristic.

In some embodiments, a method for processing an audio signal in an audio processing apparatus is disclosed. The method includes receiving an audio signal and a parameter, the parameter indicating a location of an auditory event boundary. An audio portion between consecutive auditory event boundaries constitutes an auditory event. The method further includes applying a modification to the audio signal based in part on an occurrence of the auditory event. The parameter may be generated by monitoring a characteristic of the audio signal and identifying a change in the characteristic.

A constant impedance switch dynamically manages switch impedance to eliminate or substantially reduce impedance glitches during switching events by stepping variable impedances through sequences of impedance values. As a result, VSWR may be reduced to or near 1:1, allowing programming and circuitry to be simplified. Switch impedance may be maintained for single and multi-throw switches having variable impedances of any order. Each variable impedance may comprise one or more configurable cells, subcells and elements controlled by thermometer, binary, hybrid or other coding technique.

A radio-frequency signal processing module capable of effectively removing power interference, including: a module body; a circuit board, placed inside the module body; at least one broadband system power connector electrically coupled with the circuit board; and a plurality of radio-frequency connectors electrically coupled with the circuit board for receiving at least one input radio-frequency signal and providing at least one output radio-frequency signal; wherein, the broadband system power connector has a space accommodating at least one filtering device so that interference of a power source can be attenuated and electromagnetic waves resulting from the interference can be dissipated outside the circuit board.

An apparatus for controlling the gain and phase of an input signal input to a power amplifier comprises a gain control loop configured to control the gain of the input signal based on power levels of the input signal and an amplified signal output by the power amplifier, to obtain a predetermined gain of the amplified signal, and a phase control loop configured to obtain an error signal related to a phase difference between a first signal derived from the input and a second signal derived from the amplified signal, and control the phase based on the error signal, to obtain a predetermined phase of the amplified signal. The phase control loop delays the first signal such that the delayed first signal and the second signal used to obtain the error signal correspond to the same part of the input signal. The apparatus may be included in a satellite.

The present invention is directed to electrical circuits. More specifically, embodiments of the present invention provide a variable gain amplifier (VGA) device that includes a low-gain tuning section and a high-gain tuning section. The low-gain tuning section includes both resistor and transistor elements. The high-gain tuning section includes a transistor element and is activated when an output gain is greater than a predetermined threshold level. There are other embodiments as well.