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.

This application relates to methods and apparatus for operating MEMS sensors, in particular MEMS capacitive sensors (C.sub.MEMS) such as a microphones. An amplifier apparatus (300) is arranged to amplify an input signal (V.sub.INP) received at a sense node (104) from the MEMS capacitive sensor. An antiphase signal generator (201; 304) generates a second signal (V.sub.INN) which is in antiphase with the input signal (V.sub.INP) and an amplifier arrangement (105; 305) is configured to receive the input signal (V.sub.INP) at a first input and the second signal (V.sub.INN) at a second input and to output corresponding amplified first and second output signals. This converts a single ended input signal effectively into a differential input signal.

There is provided a chopper stabilized amplifier with an input bias current reduced. The chopper stabilized amplifier includes a main amplifier and a correction circuit. The correction circuit includes a second gm amplifier of a full differential type. A first selector and the second gm amplifier are coupled to each other without DC blocking capacitors. The differential input state of the second gm amplifier is configured with a depletion-type transistor.

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.

Certain aspects of the present disclosure generally relate to a differential amplifier implemented using a complementary metal-oxide-semiconductor (CMOS) structure. The differential amplifier generally includes a first pair of transistors and a second pair of transistors coupled to the first pair of transistors. The gates of the first pair of transistors and gates of the second pair of transistors may be coupled to respective differential input nodes of the differential amplifier, and drains of the first pair of transistors and drains of the second pair of transistors may be coupled to respective differential output nodes of the differential amplifier. In certain aspects, the differential amplifier may include a biasing transistor having a drain coupled to a source of a transistor of the first pair of transistors and having a gate coupled to a common-mode feedback (CMFB) path of the differential amplifier.

The present invention relates to circuitry for voltage-to-current conversion, and in particular to differential voltage-to-current conversion circuitry. Such circuitry is operable to receive a differential voltage input signal and output a corresponding differential current signal.

An amplifier includes a differential positive input, a differential negative input, and a transistor. The transistor is communicatively coupled to the differential positive input and differential negative input at a source of the transistor. The transistor is configured to track input common mode of the differential positive input and differential negative input.

Certain aspects of the present disclosure generally relate to a differential amplifier implemented using a complementary metal-oxide-semiconductor (CMOS) structure. The differential amplifier generally includes a first pair of transistors and a second pair of transistors coupled to the first pair of transistors. The gates of the first pair of transistors and gates of the second pair of transistors may be coupled to respective differential input nodes of the differential amplifier, and drains of the first pair of transistors and drains of the second pair of transistors may be coupled to respective differential output nodes of the differential amplifier. In certain aspects, the differential amplifier may include a biasing transistor having a drain coupled to a source of a transistor of the first pair of transistors and having a gate coupled to a common-mode feedback (CMFB) path of the differential amplifier.

A circuit for amplifying signals from a Micro Electro-Mechanical System (MEMS) capacitive sensor is provided. First and second input nodes receive a sensing signal applied differentially between the input nodes. A first amplifier stage and a second amplifier stage, respectively, produce a differential output signal between first and second output nodes. A common mode signal is detected at the output nodes. A voltage divider having an intermediate tap node is coupled between the first output node and the second output node. A feedback stage is coupled between the intermediate tap node of the voltage divider and the inputs of the first amplifier stage and the second amplifier stage, where the feedback line is sensitive to the common mode signal at the output nodes.

An amplifier that amplifies a differential signal includes first and second input terminals for receiving two input signals; first and second diodes each including an anode and a cathode, the anodes being electrically connected to the first and second input terminals; first and second bias current sources being respectively electrically connected to the cathodes of the first and second diodes; an operational amplifier connected to the cathode of the first diode and the cathode of the second diode and configured to amplify a differential signal between signals generated at the cathodes of the first and second diodes; a capacitive element being electrically connected between an input and an output of the operational amplifier; and a differential amplifier provided between the operational amplifier and the first and second input terminals and configured to amplify the two input signals. The first and second bias current sources include a current mirror circuit.