A semiconductor device includes a differential amplification circuit that outputs differential output signals Vo1 and Vo2, external output terminals PD1 and PD2 to which one of the differential output signals Vo1 and Vo2 and single end signals Vo3 and Vo4 is selectively supplied, switch units SW1 and SW2 that control a conduction state between the external output terminal PD1 and the feedback line and a conduction state between the external output terminal PD2 and the feedback line, respectively, resistance elements R1 and R2 respectively provided in series with the switch units SW1 and SW2, a CMFB circuit that controls a common mode voltage of the differential amplification circuit according to a difference between an intermediate voltage Vcm of the external output terminals PD1 and PD2 in the feedback line and a reference voltage Vref, and a switch unit SW3 that controls to supply a clamp voltage to the feedback line.

A programmable a fully-differential programmable gain amplifier for reducing distortion, switching transients and interference, and improving bandwidth. In one embodiment, the amplifier includes a programmable gain module, an amplifier coupled to the current mode outputs and a data latch circuit of the programmable gain module, the amplifier configured to apply common mode voltage to the data latch circuit, and a current-to-voltage converter. In one embodiment, the fully-differential programmable gain amplifier controls distortion and switching interference during amplification by sensing common mode signals to produce an error signal, and applying the resulting error signal to the programmable gain module for multiplying digital to analog conversion. Components of the fully-differential programmable gain amplifier provide compensation of distortion caused by nonlinearity of device switches and switch resistance, and can include a floating supply, galvanic isolation of control signals and a common mode voltage controller.

A Low-Voltage Differential Signaling (differential signaling) driver circuit (10) comprising enable circuitry for enabling and disabling the differential signaling driver circuit (10) in accordance with an control signal is described. The differential signaling driver circuit (10) comprises: a differential output (12, 13) connected or connectable to a differential signaling receiver circuit via a differential transmission line; current control circuitry (14) for driving a signal current through the differential output (12, 13) in accordance with a driver signal; feedback circuitry (16) for driving the current control circuitry (14) to counteract a difference between a common mode voltage of the differential output (12, 13) and a reference voltage from a reference voltage provider; and the enable circuitry (18). The feedback circuitry (16) comprises a common mode node (20) for providing the common mode voltage (Vcm), a reference input (22) connected or connectable to the reference voltage provider, and a feedback input (24). The enable circuitry (18) is arranged to connect the feedback input (24) to the common mode node (20) when the differential signaling driver circuit (10) is in an enabled state and to the reference voltage provider when the differential signaling driver circuit (10) is in a disabled state. A method of enabling (5.1) and disabling (5.2) a Low-Voltage Differential Signaling (differential signaling) driver circuit (10) is also proposed.

An amplifier circuit. In some embodiments, the amplifier circuit includes: a telescopic amplifier, and a common mode feedback amplifier. The telescopic amplifier has a first signal input, a second signal input, a first output, a second output, a common mode feedback input, a first pole-splitting capacitor, and a second pole-splitting capacitor. The common mode feedback amplifier has an output connected to the common mode feedback input of the telescopic amplifier. The first pole-splitting capacitor is connected between the common mode feedback input of the telescopic amplifier and the first output of the telescopic amplifier, and the second pole-splitting capacitor is connected between the common mode feedback input of the telescopic amplifier and the second output of the telescopic amplifier.

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.

An impedance circuit includes a first poly-resistor and a second poly-resistor. The first poly-resistor has a first terminal coupled to a first node, and a second terminal coupled to a second node. The second poly-resistor has a first terminal coupled to the first node, and a second terminal coupled to the second node. The resistance between the first terminal and the second terminal of the first poly-resistor is determined according to a first control voltage. The resistance between the first terminal and the second terminal of the second poly-resistor is determined according to a second control voltage. The first control voltage and the second control voltage are determined according to a first voltage at the first node and a second voltage at the second node.

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.

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 is arranged to amplify an input signal (V.sub.INP) received at a sense node from the MEMS capacitive sensor. An antiphase signal generator generates a second signal (V.sub.INN) which is in antiphase with the input signal (V.sub.INP) and an amplifier arrangement 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.

An amplifier circuit having improved common mode rejection is provided. This can be achieved by estimating the common mode value of an input signal and using this to adjust a target common mode voltage at the output of the amplifier. This can help avoid the differential gain becoming modified by the common mode voltage.

A common mode feedback (CMFB) loop for a differential amplifier sense an output common mode of a differential circuit and provides feedback to the gates of tail current transistors. Many CMFB loops cannot easily adjust the output common mode voltage and the output common mode may vary over process, voltage, and temperature. An improved CMFB circuit adds a control circuit to control backgates of tail current transistor device(s) of the differential circuit such that the output common mode voltage can be made adjustable.