A sensor arrangement comprises a sensor having a first terminal and a second terminal, and an amplifier having an amplifier input for applying an input signal and an amplifier output for providing an amplified input signal, the amplifier input being coupled to the second terminal. The sensor arrangement further comprises a quantizer having a quantizer input and a quantizer output being suitable for providing a multi-level output signal on the basis of the amplified input signal and a feedback circuit having a feedback circuit input coupled to the quantizer output and a feedback circuit output coupled to the first terminal. The feedback circuit comprises a digital-to-analog converter being suitable for generating an analog signal on the basis of the multi-level output signal, the analog signal being the basis of a feedback signal provided at the feedback circuit output. The feedback circuit further comprises a feedback capacitor that is coupled between the feedback circuit output and an output of the digital-to-analog converter, and a voltage source coupled to the feedback circuit output.

Transimpedance amplifiers with feedforward current are provided herein. In certain embodiments, an amplifier system includes a transimpedance amplifier that amplifies an input current received at an input to generate an output voltage at an output. The amplifier system further includes a controllable current source that is coupled to the output of the transimpedance amplifier, and operable to provide a feedforward current that changes in relation to the input current of the transimpedance amplifier. By providing a feedforward current in this manner, gain and speed performance of the transimpedance amplifier is enhanced.

An impedance measurement circuit for determining a sense current of a guard-sense capacitive sensor operated in loading mode. The circuit includes a periodic signal voltage source for providing a periodic measurement voltage, a sense current measurement circuit, a differential amplifier that is configured to sense a complex voltage difference between the sense electrode and the guard electrode, a demodulator for obtaining, with reference to the periodic measurement voltage, an in-phase component and a quadrature component of the sensed complex voltage difference, and control loops for receiving the in-phase component and the quadrature component, respectively. An output signal of the first control loop and an output signal of the second control loop are usable to form a complex voltage that serves as a complex reference voltage for the sense current measurement circuit.

A power amplifier circuit includes a first transistor, a capacitor, and a second transistor. The first transistor has an emitter electrically connected to a reference potential, a base, and a collector electrically connected to a first power supply potential. A first end of the capacitor is electrically connected to the collector of the first transistor. The second transistor has an emitter electrically connected to a second end of the capacitor and electrically connected to the reference potential, a base, and a collector electrically connected to the first power supply potential. An RF output signal obtained by amplifying the RF input signal is output from the collector of the second transistor. A second bias circuit includes a third transistor having a collector electrically connected to a second power supply potential, a base, and an emitter from which the second bias current or voltage is output.

Embodiments provide a power management system for a battery-powered audio device. The system includes bi-directional power conversion and control circuitry to implement a corresponding control scheme. The system may be switchable between a charge mode, during which the power conversion and control circuitry charges the battery of the audio device and the AC/DC adapter provides an amplifier supply voltage to one or more amplifiers of the audio device, and a discharge mode, in which the power conversion and control circuitry may provide a regulated amplifier supply voltage to the one or more amplifiers that is regulated based on one or more operating conditions of the system. The system may provide reduced cost and reduced power consumption and reduced size compared with prior systems.

A cascade of amplifier stages has a differential input and a differential output. The cascade of amplifier stages includes at least one differential amplifier circuit including first and second transistors, at least one of the first and second transistors having a control terminal and a body terminal. A mismatch between the first and second transistors generates an input offset. A feedback network couples the differential output to the body terminal in order to cancel the input offset. The feedback network includes a low-pass filter and a differential amplifier stage.

An amplifier for a receiver circuit is disclosed. The amplifier has an input node (V.sub.in) and an output node (V.sub.out). It comprises a tunable tank circuit connected to the output node (V.sub.out), a feedback circuit path connected between the output node (V.sub.out) and the input node (V.sub.in), and a tunable capacitor connected between an internal node of the feedback circuit path and a reference-voltage node. A receiver circuit and a communication apparatus is disclosed as well.

An error amplifier for a pulse width modulation circuit is described. The amplifier includes an operational amplifier configured as an integrator and a feedback loop coupled between a signal output of the operational amplifier and an inverting input of the operational amplifier. The feedback loop comprises a feedback capacitor coupled to the signal output, a feedback resistor coupled to the feedback capacitor, and an integrator resistor coupled to the feedback resistor and the inverting input of the operational amplifier. A junction between the feedback resistor and the integrator resistor is configured to receive an input signal and a junction between the feedback capacitor and the feedback resistor is configured to receive a feedback signal from the pulse width modulation circuit.

An integrated circuit, comprising an amplifier comprising a pair of inputs configured to receive a differential signal, a first resistor, a second resistor, wherein the first resistor and the second resistor are coupled in series with each other and coupled to a first input of the pair of inputs, a third resistor, a fourth resistor, wherein the third resistor and the fourth resistor are coupled in series with each other and coupled to a second input of the pair of inputs, and a first capacitor comprising a first end coupled to a first point between the first resistor and the second resistor, and a second end coupled to a second point between the third resistor and the fourth resistor, a second capacitor disposed between the first input and an output of the amplifier; and a third capacitor disposed between the second input and the output.

Frequency selective analog front-end circuitry, used to convert a sensed charge signal to an analog voltage is disclosed. In one aspect, the frequency selective analog front-end circuitry includes an op-amp having an output, an inverting input and a noninverting input, a first resistor connected between the terminal of the first capacitor and the inverting input of the op-amp, a second capacitor connected between the output of the op-amp and the inverting input of the op-amp, a second resistor connected between the output of the op-amp and the inverting input of the op-amp, a third capacitor connected between the terminal of the first capacitor and the noninverting input of the op-amp, and a third resistor connected between the noninverting input of the op-amp and a reference voltage.