An operational amplifier includes: a first amplifier stage, configured to generate first output voltages according to first input voltages; a second amplifier stage, configured to generate second output voltages according to the first output voltages; a second output stage circuit, configured to replicate an equivalent or a scaled-down version of the first output stage circuit; a first common-mode feedback circuit, configured to keep an output common-mode voltage of the second output stage circuit at a predetermined value; a logic loop circuit configured to, when the operational amplifier operates in a direct current calibration phase, adjust a difference between the first output voltages; a bias circuit, configured to generate a voltage close to a common mode voltage of the first output voltages produced after the operational amplifier is turned on, the voltage serving as a reference voltage of a second common-mode feedback circuit.

A circuit system including an operational amplification circuit is disclosed. The operational amplification circuit includes N stages of operational amplification units that are cascaded, an input terminal of the 1.sup.st stage of operational amplification unit is an input terminal of the operational amplification circuit, and an output terminal of the N.sup.th stage of operational amplification unit is an output terminal of the operational amplification circuit; an output terminal of the i.sup.th stage of operational amplification unit is connected to an input terminal of the (i+1).sup.th stage of operational amplification unit, so as to provide an input signal for the (i+1).sup.th stage of operational amplification unit; and there is a feedback channel from the output terminal of the N.sup.th stage of operational amplification unit to an input terminal of each of the 1.sup.st stage of operational amplification unit to the N.sup.th stage of operational amplification unit.

A circuit includes a first integration stage, a quantizer, a second integration stage coupled between the first integration stage and the quantizer, and a digital-to-analog converter (DAC). The first integration stage includes a first input node pair configured to receive a pair of differential analog input signals, and the quantizer is configured to generate a digital signal based on the pair of differential analog input signals and a clock signal. The second integration stage includes a second input node pair, and the DAC is configured to receive the digital signal and output feedback signals to at least one input node pair of the first input node pair or the second input node pair.

The invention relates to a broadband high power amplifier that comprises a signal input adapted to receive an input signal, at least one amplifier stage adapted to amplify the received input signal, a signal output adapted to output the signal amplified by the at least one amplifier stage as an output signal, a monitoring unit adapted to monitor signal characteristics of the input signal and the output signal and a control unit adapted to operate the at least one amplifier stage at an optimal operating point depending on the current signal characteristics monitored by said monitoring unit.

The disclosed technology relates to a method for improving performance of a feedback circuit comprising an amplifier and a feedback network, wherein the feedback circuit has at least one tunable component. In one aspect, the method comprises measuring first amplitude values at an input of the amplifier and second amplitude values at an output of the amplifier, estimating a linear open-loop gain of the amplifier based on both the amplitude values, estimating a linear finite gain error based on the estimated gain and the second amplitude values, subtracting the linear finite gain error from the first amplitude values to derive a set of samples containing second error information, deriving an signal-to-noise-plus-distortion ratio estimate based on the variance of the set of samples and a variance of the second amplitude values, and adjusting the feedback circuit in accordance with the signal-to-noise-plus-distortion ratio estimate.

A power amplifier includes a two-dimensional matrix of NM active cells formed by stacking main terminals of multiple active cells in series. The stacks are coupled in parallel to form the two-dimensional matrix. The power amplifier includes a driver structure to coordinate the driving of the active cells so that the effective output power of the two-dimensional matrix is approximately NM the output power of each of the active cells.

In one general aspect, an amplifier can include an input amplifier circuit configured to receive a bias current and receive, as an input, a signal pair connected differentially to the input amplifier circuit, the input amplifier circuit configured to output a differential output signal pair based on the received differential input signal pair, a feedback amplifier circuit configured to receive an average of the differential output signal pair and configured to provide a bias setting output for controlling the bias current, and an output buffer circuit configured to buffer the differential output signal pair, the buffering resulting in a buffered differential output signal pair capable of driving a resistive load.

A microphone assembly comprising: a housing including a base, a cover, and a sound port; a MEMS transducer element disposed in the housing, the transducer element configured to convert sound into a microphone signal voltage at a transducer output; and a processing circuit. The processing circuit comprising a transconductance amplifier comprising an input node connected to the transducer output for receipt of the microphone signal voltage, the transconductance amplifier being configured to generate an amplified current signal representative of the microphone signal voltage in accordance with a predetermined transconductance of the transconductance amplifier; and an analog-to-digital converter comprising an input node connected to receive the amplified current signal, said analog-to-digital converter being configured to sample and quantize the amplified current signal to generate a corresponding digital microphone signal.

The operational amplifier disclosed includes an input stage configured to receive power from a floating supply in a low voltage range that can float according to the common mode voltage at the input. The floating supply facilitates the use of low voltage components that can improve the precision of the operational amplifier by lowering the offset voltage. The input stage includes a first gain stage including field effect transistors and a second gain stage using bipolar transistors. The gain stages can be implemented differently to accommodate different applications and fabrication capabilities.

A class-D amplifier with multiple nested levels of feedback. The class-D amplifier surrounds an inner feedback loop, which takes the output of a switching amplifier and corrects for errors generated across the switching amplifier, with additional feedback loops that also take the output of the switching amplifier.