A radio frequency (RF) power amplifier circuit with a diode linearizer circuit. The power amplifier circuit has an input and an output, as well as a power amplifier transistor with a first terminal connected to the input, a second terminal connected to the output, and a third terminal. The linearizer circuit is connected to the third terminal and to ground, and has a non-linear current-voltage curve as well as a non-linear capacitance. The linearizer circuit reduces inter-modulation products in a current through the power amplifier transistor from the second terminal to the third terminal that corresponds to an input signal applied to the input.

The use of a capacitor (22) to serve as the principal impedance in a negative feed-back loop in a voltage amplifier component (21) of a trans-impedance amplifier and actively controlling the amount of charge accumulated within the capacitor appropriately to improve the responsiveness and/or dynamic range of the amplifier. A switch (25) is electrically coupled to the inverting input terminal of the voltage amplifier and electrically isolated from the output terminal (23) of the voltage amplifier. The output voltage of the amplifier is proportional to the accumulation of charge, and the switch is operable to reset the charge/voltage on the feedback capacitor, as desired. This arrangement decouples the structure of the switch from the output port of the voltage amplifier, and so avoids leakage currents and/or interfering voltage signals emanating from the switch structure and being felt at the output port of the voltage amplifier.

A capacitive trans-impedance amplifier comprising a voltage amplifier having an inverting input terminal for connection to an input current source. A feed-back capacitor is coupled between the inverting input terminal and the output terminal to accumulate charges received from the input current source and to generate a feed-back voltage accordingly. A calibration unit includes a calibration capacitor electrically coupled, via a calibration switch, to the inverting input terminal and electrically coupled to the feed-back capacitor. The calibration unit is operable to switch the calibration switch to a calibration state permitting a discharge of a quantity of charge from the calibration capacitor to the feed-back capacitor. The capacitive trans-impedance amplifier is arranged to determine a voltage generated across the feed-back capacitor while the calibration switch is in the calibration state and to determine a capacitance value (C=Q/V) for the feed-back capacitor according to the value of the generated voltage (V) and the quantity of charge (Q).

An amplifier circuit (AC) for amplifying an output signal (OS) of a capacitive sensor (M) comprises a first input terminal (AIN) to receive the output signal (OS) of the capacitive sensor (M) and a second input terminal (BIN) to receive a bias voltage (Vbias) of the capacitive sensor (M). The amplifier circuit (AC) comprises an amplifier (A) for amplifying the output signal (OS) and a control circuit (CF) arranged in a feedback loop (FL) of the amplifier (A) being configured to control a DC voltage level at an input connection (A1) of the amplifier (A). A bias voltage sensing circuit (BVS) senses a change of the level of the bias voltage (Vbias) at the second input terminal (BIN) and changes the bandwidth of the feedback loop (FL) in dependence on the sensed change of the level of the bias voltage (Vbias).

A structure having: a plurality of field effect transistors (FETs) connected between a common input and a common output, each one of the field effect transistors comprises: a source region, a drain region, and a gate electrode for controlling carriers through a channel region of a transistor region of the structure between the source region and the drain region; a plurality of diodes, each one of the diodes being associated with a corresponding one of the plurality of FETs, each one of the diodes having an electrode in Schottky contact with a diode region of the corresponding one of the FETs. The gate electrode and the diode electrode extend along parallel lines. The source region, the drain region, the channel region, and a diode region having therein the diode are disposed along a common line.

A radio frequency (RF) power amplifier circuit with a diode linearizer circuit. The power amplifier circuit has an input and an output, as well as a power amplifier transistor with a first terminal connected to the input, a second terminal connected to the output, and a third terminal. The linearizer circuit is connected to the third terminal and to ground, and has a non-linear current-voltage curve as well as a non-linear capacitance. The linearizer circuit reduces inter-modulation products in a current through the power amplifier transistor from the second terminal to the third terminal that corresponds to an input signal applied to the input.

An amplifier includes an input circuit, an amplification circuit, and at least two feedback circuits. The input circuit is connected with an input end of the amplification circuit; an output end of the amplification circuit is connected with a first end of each of the feedback circuits respectively; a second end of each of the feedback circuits is connected with the input circuit respectively. The input circuit is configured to receive an input signal and a feedback signal; the amplification circuit is configured to amplify the input signal and the feedback signal to obtain an amplified signal. The feedback signal is fed back to the input circuit by feeding back at least a part of the amplified signal through a target feedback circuit; and the target feedback circuit is a feedback circuit that depends on the type of the input signal of the at least two feedback circuits.

A current detection circuit has a differential amplification circuit that outputs a differential output current dependent on a voltage difference between input terminals and first and second feedback circuits that output a detection current in response to the differential output current and form a feedback path to each input terminal of the differential amplification circuit. First and second MOS transistors that generate voltages dependent on respective source-drain voltages at a time when drain currents in a forward direction and a backward direction flow through an output MOS transistor are connected to respective input terminals of the differential amplification circuit.

An automatic gain control (AGC) transimpedance amplifier (TIA) uses a differential structure with feedback PIN diodes to adjust the loop gain of the amplifier automatically to maintain stability over a wide dynamic range when converting optical power using a photodiode to an electrical signal. A stable DC current derived from the photodiode current sets the voltage gain of the amplifier. The use of ultra-linear long carrier lifetime PIN diodes assures the transimpedance feedback resistance is linear. The AGC function adjusts the gain of the TIA to provide a linear stable differential transresistance controlled by the photodiode current; a linear stable AGC function using current supplied by the photodiode; an improvement of about 10 db of the transresistance dynamic range; and reduces the need for internal and external circuitry needed to provide the same function. The TIA is applicable to CATV optical systems which have very strict linearity requirements.

An amplifier assembly (100) includes an amplifier (102) having an input terminal, an output terminal and a feedback terminal; a first feedback path connecting the output terminal to the feedback terminal; a second feedback path connecting the output terminal to the feedback terminal; a switch (124) positioned in the second feedback path, the switch (124) opening or closing in response to a voltage at the output terminal relative to a breakpoint, when the switch (124) is open, the amplifier assembly (100) has a first gain and when the switch (124) is closed, the amplifier assembly (100) has a second gain; and a thermally variable element (152) connected to the switch (124), the thermally variable element (152) configured to generate a compensation voltage to maintain the breakpoint in response to varying temperature of the switch (152).