A power amplifier circuit includes a first transistor amplifying a first signal; a second transistor amplifying a second signal; a bias circuit supplying a bias current or voltage to a base or gate of the second transistor; and an attenuator attenuating the first or second signal in accordance with a control voltage supplied from the bias circuit. The attenuator includes a first diode to which the control voltage is supplied, a third transistor including a collector connected to a supply path of the first or second signal, an emitter connected to a ground, and a base to which the control voltage is supplied from the first diode, and a capacitor connected in parallel with the first diode. The control voltage decreases as a second signal power level increases. The third transistor allows part of the first or second signal to pass to the emitter in accordance with the control voltage.

The invention relates to a gain-control stage (100) for generating gain-control signals (V.sub.c+, V.sub.c) for controlling an external variable-gain amplifying unit (101). The gain-control stage comprises a first (102) and a second differential amplifier unit (112) that receive, at a respective input interface (104,114) a reference voltage signal (V.sub.Ref) and a variable gain-control voltage signal (V.sub.GC). The second differential amplifier unit is configured to provide, via a second output interface (120), a control voltage signal (V.sub.1) to a controllable first current source (106) of the first differential amplifier unit (102). The first differential amplifier unit (102) is configured to provide, via a first output interface (110), the first and the second gain-control signal (V.sub.C+, V.sub.C) in dependence on the variable gain-control voltage signal (V.sub.GC), the reference voltage signal (V.sub.Ref) and a first biasing current (I.sub.B1) that depends on the control voltage signal.

Biasing circuitry for RF and microwave integrated circuits keeps the quiescent current of a power amplifier integrated circuit constant when operated with a time-varying DC supply voltage. A dynamic gate bias circuit includes an on-chip sense transistor and control circuitry to keep current of the sense transistor substantially constant by varying sense transistor bias voltage to compensate for variation in the time-varying supply voltage signal. The varying bias voltage is then applied to the amplifying transistors of the power amplifier, resulting in their quiescent current being substantially independent of the time-varying supply voltage.

Wideband signal buffers that can be employed for mmWave (millimeter wave) communication are disclosed. One example signal buffer comprises a variable gain amplifier (VGA) that receives two control words and outputs a feedback signal, wherein both an amplitude and a phase of the feedback signal are based on the two control words and on a bias voltage; and a matching network comprising a first inductor that outputs the bias voltage, a second inductor, and a third inductor that receives the feedback signal from the VGA, and wherein the first, second, and third inductors are magnetically coupled to each other, wherein the signal buffer is configured to receive a RF (Radio Frequency) input and to generate a RF output from the RF input based on a transfer function of the signal buffer, wherein the transfer function is based at least in part on the feedback signal.

Described herein are systems and methods that can adjust the performance of a transimpedance amplifier (TIA) in order to compensate for changing environmental and/or manufacturing conditions. In some embodiments, the changing environmental and/or manufacturing conditions may cause a reduction in beta of a bipolar junction transistor (BJT) in the TIA. A low beta may result in a high base current for the BJT causing the output voltage of the TIA to be formatted as an unusable signal output. To compensate for the low beta, the TIA generates an intermediate signal voltage, based on the base current and beta that is compared with the PN junction bias voltage on another BJT. Based on the comparison, the state of a digital state machine may be incremented, and a threshold base current is determined. This threshold base current may decide whether to compensate the operation of the TIA, or discard the chip.

A multimode power amplifier module, a chip and a communication terminal. In the module, a control circuit (104) sends a bias signal to a low-frequency power amplifier (102) or a high-frequency power amplifier (106) according to a baseband signal, so as to control the amplification of an accessed low-frequency radio frequency signal or a high-frequency radio frequency signal by the low-frequency power amplifier (102) or the high-frequency power amplifier (106); and a transceiving switch (108) selects a corresponding operation mode to conduct transmission or receiving according to an operation mode selection signal. A power amplification path is reused according to different modes, so that the power amplification path can be shared by different operation modes of a high and low frequency band with the adjustment of the control circuit (104), thus simplifying the complexity in designing the power amplifier module, and reducing the cost of relevant design implementation.

A differential amplifier generates an output voltage waveform exhibiting a slew rate over a rise time. The amplifier is powered from a dc voltage input and includes a set of differential pairs having a bias current flowing therethrough and a Miller compensation capacitance. A comparator functions to compare a voltage at the dc voltage input against a reference voltage in order to detect when the voltage drops below the reference voltage. A gain stage controls the gain of the differential amplifier and a bias current control circuit controls the bias current of the differential amplifier. In response to the detection by the comparator of the voltage dropping below the reference voltage, the gain stage and the bias current control circuit decrease the gain of the amplifier and jointly decrease the bias current in order to maintain a value of the rise time.

The present disclosure relates to a power amplifier (PA) system provided in a semiconductor device and having feed forward gain control. The PA system comprises a transmit path and control circuitry. The transmit path is configured to amplify an input radio frequency (RF) signal and comprises a first tank circuit and a PA stage. The control circuitry is configured to detect a power level associated with the input RF signal and control a first bias signal provided to the PA stage based on a first function of the power level and control a quality factor (Q) of the first tank circuit based on a second function of the power level.

An apparatus for detecting a neural spike includes: a preprocessing circuit configured to remove a low-frequency component from a neural signal to form a low-frequency component removed neural signal, and amplify the low-frequency component removed neural signal; a comparing circuit configured to compare an output signal of the preprocessing circuit to a threshold signal; a merging circuit configured to merge spikes within a reference interval of an output signal of the comparing circuit into one peak, and to generate, based on the merging of the spikes, an output signal comprising pulses; and a counting circuit configured to count the pulses.

Systems and techniques are generally described for audio signal processing for motion detection. In some examples, a first energy level of a first audio signal detected by a first microphone is determined over a first period of time. In some further examples, a first change in the first energy level from a first energy level value to a second energy level value is determined during the first period of time. In some other examples, a determination is made that the first change in the first energy level exceeds a threshold change value associated with the first period of time. In at least some other examples, a bias of an audio amplifier of the first device is adjusted.