According to one aspect, embodiments of the invention provide a distortion detection circuit comprising an input configured to be coupled to an output stage of an amplifier and to receive an RF signal from the output stage of the amplifier, an output configured to be coupled to a module of the amplifier, at least one peak detection circuit coupled to the input and configured to monitor the RF signal and output a first signal based on positive voltage peaks of the RF signal, and a differential amplifier having an input coupled to the at least one peak detection circuit and configured to monitor the first signal and provide a second signal to the output in response to a voltage of the first signal exceeding a threshold level indicative of distortion in the RF signal.

A sensor amplifier arrangement includes an amplifier having a signal input to receive a sensor signal and a signal output, and a feedback path that couples the signal output to the signal input, wherein the feedback path includes an anti-parallel circuit of diodes, and a voltage divider including a first and a second divider resistor and a voltage divider tap between the first and the second divider resistor, wherein the voltage divider couples the signal output to a reference potential terminal, and the voltage divider tap is coupled to the anti-parallel circuit of diodes and the anti-parallel circuit of diodes is coupled to the signal input.

Radio Frequency (RF) amplifiers with voltage limiting using non-linear feedback are presented herein. According to one aspect, an RF amplifier comprises an amplifier circuit having an input terminal and an output terminal and a non-linear feedback circuit having an input terminal and an output terminal. The input terminal of the non-linear feedback circuit is connected to the output terminal of the amplifier circuit and the output terminal of the non-linear feedback circuit is connected to the amplifier circuit to reduce the gain of the amplifier circuit when an RF voltage swing present at the input terminal of the non-linear feedback circuit exceeds a predefined threshold. In one embodiment, the output terminal of the non-linear feedback circuit is connected to the input terminal of the amplifier circuit. In another embodiment, the output terminal of the non-linear feedback circuit is connected to a bias circuit of the amplifier circuit.

The invention discloses a nonlinear feedback circuit, which includes at least one diode. The invention also discloses a low noise amplifier using the nonlinear feedback circuit. In the invention, temperature compensation is performed for the gain change of the low noise amplifier based on the negative temperature characteristics of the diode, thereby achieving gain stability. In addition, the nonlinear characteristics of the diode can also provide high-order harmonics for the low-noise amplifier, and the mutual cancellation and addition of high-order harmonics can increase the OIP3 of the low noise amplifier.

Provided is a preamplifying circuit, including a first amplifier and a second amplifier sequentially connected in series, wherein an output end of the second amplifier is connected to a circuit output end, and an input end of the first amplifier is connected to a circuit input end. The preamplifying circuit further includes a positive feedback branch including a diode group and a third amplifier, wherein one end of the diode group is connected to the input end of the first amplifier. The positive feedback circuit can positively feed part of signals back to the other end of the diode group, so that voltage drops at two ends of the diode group can be reduced, and harmonic distortion caused by nonlinearity of the diode group is reduced. Thus, the sound quality detected by a microphone sensor is improved.

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.

Provided is a sensor interface including a first cantilever beam bundle including at least one resonator and a first output terminal, a second cantilever beam bundle including at least one resonator and a second output terminal, and a differential amplifier including a first input terminal electrically connected to the first output terminal of the first cantilever beam bundle and a second input terminal electrically connected to the second output terminal of the second cantilever beam bundle.

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).

A control system is configured to control an output power of a power amplifier. The control system is operable to detect when the power amplifier is in first state and responsively provide first additional bias to the power amplifier. The first additional bias assists or enables the power amplifier in increasing the output power. The control system is also operable to detect when the power amplifier is in a second state and responsively provide second additional bias to the power amplifier. The second additional bias assists or enables the power amplifier in increasing the amount of output power.

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).