A circuit for filtering a signal corresponding to a time of flight (TOF) of light from a laser reflected off an object to a photo detector, the circuit includes a preamplifier, a DC cancelation loop, and an AC cancelation loop. The preamplifier may be configured to receive the signal from the photo detector corresponding to an output of the laser reflected off an object remote from the laser and photo detector. The DC cancelation loop includes a current feedback DC servo loop. The AC cancelation loop includes a feedback network driven by a floating class AB output stage, and the preamplifier configured to drive the floating class AB output stage, wherein the preamplifier is driven by an error signal of the feedback network and creates an AC signal path with the feedback network and floating class AB output stage.

An ECG signal acquisition system includes a first amplifier which has a non-inverting input adapted to be coupled to a first differential input, an inverting input adapted to be coupled to a second differential input, and an output. The system includes first and second biasing resistors coupled between the non-inverting and inverting inputs of the first amplifier. The system includes an average estimation circuit which has a first input coupled to the non-inverting input of the first amplifier and a second input coupled to the inverting input of the first amplifier. The system includes a driver amplifier which has an inverting input coupled to the output of the average estimation circuit, a non-inverting input coupled to receive a reference common-mode voltage, and an output. The system includes a low-pass filter coupled between the output of the driver amplifier and the biasing resistors.

A variable-current trans-impedance amplifier (TIA) for an ultrasound device is described. The TIA may be coupled to an ultrasonic transducer to amplify an output signal of the ultrasonic transducer representing an ultrasound signal received by the ultrasonic transducer. During acquisition of the ultrasound signal by the ultrasonic transducer, one or more current sources in the TIA may be varied. The variable-current trans-impedance amplifier may include multiple stages, including a first stage having N-P transistor pairs configured to receive an input signal and produce a single-ended amplified signal.

The semiconductor device includes a Hall element, a first differential pair, a second differential pair, an output amplifier circuit, and a voltage divider circuit. The Hall element outputs a signal that is dependent on stress to be applied to a semiconductor substrate to the first differential pair. The voltage divider circuit divides a voltage into a divided voltage having a voltage dividing ratio that is dependent on the stress. The first differential pair outputs a first current based on the signal. The second differential pair outputs a second current based on the divided voltage and a reference voltage. The output amplifier circuit outputs a voltage based on the first and second currents. A gain of the output amplifier circuit is approximated by a sum of a difference between stress dependence coefficients of transconductances of the first and second differential pairs and a stress dependence coefficient of the voltage dividing ratio.

In certain aspects, a method is provided for measuring power using a resistive element coupled between a power amplifier and an antenna. The method includes squaring a voltage from a first terminal of the resistive element to obtain a first signal, squaring a voltage from a second terminal of the resistive element to obtain a second signal, and generating a measurement signal based on a difference between the first signal and the second signal. In some implementations, the resistive element is implemented with a power switch.

A method includes determining one or more characteristics of a system that uses a power amplifier. The method also includes determining, based on the one or more determined characteristics, a switching speed and a supply voltage for the power amplifier. The method further includes modulating a power supply of the power amplifier according to the determined switching speed and supply voltage.

A balanced differential transimpedance amplifier with a single-ended input operational over a wide variation in the dynamic range of input signals. A threshold circuit is employed to either or a combination of (1) generate a varying decision threshold to ensure a proper slicing over a wide range of input current signal levels; and (2) generate a bias current and voltage applied to an input of a transimpedance stage to cancel out a dependence of the transimpedance stage voltage input on input current signal levels.

In one implementation, a circuit can include a reference pin and an operational amplifier that can include an output pin, an inverting input pin and a non-inverting input pin. The inverting input pin can be electrically coupled to the output pin via a first impedance and to the reference pin via a second impedance. The non-inverting input pin can be electrically coupled to the reference pin via a third impedance and can be configured to receive a detection signal. The reference pin can be configured to receive a detection reference signal associated with the detection signal.

An audio amplifier circuit for providing an output signal to an audio transducer may include a power amplifier and a control circuit. The power amplifier may include an audio input for receiving an audio input signal, an audio output for generating the output signal based on the audio input signal, and a power supply input for receiving a power supply voltage, wherein the power supply voltage is variable among at least a first supply voltage and a second supply voltage greater than the first supply voltage. The control circuit may be configured to predict, based on one or more characteristics of a signal indicative of the output signal, an occurrence of a condition for changing the power supply voltage, and responsive to predicting the occurrence of the condition, change, at an approximate zero crossing of the signal indicative of the output signal, the power supply voltage.

In accordance with embodiments of the present disclosure a control circuit may include at least one input for monitoring a respective signal for each of a plurality of amplifiers, an output for outputting at least one control signal for controlling a power supply level of the single signal-variant power supply configured to deliver electrical energy to the plurality of amplifiers, and decision and control logic. The decision and control logic may be configured to monitor the respective signals for each of the plurality of amplifiers and, based on the respective signals, and a respective requirement associated with each of the plurality of amplifiers, setting a power supply level of the single signal-variant power supply and outputting the at least one control signal to control the power supply level such that the respective requirements are satisfied.