A phase rotator apparatus has phase interpolation and transimpedance amplifier (TIA) stages. This separates gain and bandwidth as degrees of design freedom, facilitating a reduction in power consumption while enabling the data link to transmit and receive higher speed data. Four phases of an incoming signal are combined by the phase interpolation stage using weighting currents and current-source loads to produce a phase shifted current based signal that the TIA stage receives as input. The TIA stage then converts the signal to a voltage based signal. The quiescent operating voltage of the stage outputs can be maintained with common mode feedback circuits and injector currents.

An apparatus for detecting optical signals includes a photodetector. The photodetector is reverse-biased by a first voltage and a second voltage is added to the first voltage to provide an offset equal to the second voltage for the photodetector. A first circuit is coupled to the first circuit to provide the second voltage for the photodetector and a second circuit is coupled to the first circuit to provide the first voltage to the photodetector to reverse-bias the photodetector. The second circuit provides an output voltage proportional to a current of the photodetector at an output of the second circuit.

Described examples include multistage amplifier circuits having first and second forward circuits, a comparator or sensor circuit coupled to sense a signal in the second forward circuit to identify nonlinear operation or slewing conditions in the multistage amplifier circuit, and one or more sample hold circuits operative according to a sensor circuit output signal to selectively maintain the amplitude of an amplifier input signal in the second forward circuit and/or in a feedback circuit in response to the sensor circuit output signal indicating nonlinear operation or slewing conditions in the multistage amplifier circuit. Certain examples further include a clamping circuit operative to selectively maintain a voltage at a terminal of a Miller compensation capacitance responsive to the comparator output signal indicating nonlinear operation or slewing conditions.

An analog-to-digital converter (ADC) may include capability to sense and/or compensate for undesired effects when receiving input from a microphone. For example, a sense node may be provided between differential inputs, and that sense node separated from the differential inputs by two or more switches. The sense node may allow for a measurement of an average voltage of the differential inputs. The average voltage may be obtained activating the switches to sample the sampling capacitors coupled to the differential inputs. That average voltage may be used as common mode (CM) data. A controller may receive the CM data, along with differential mode (DM) data, and use the CM and DM data to determine undesired effects, such as DC or AC mismatch at the microphone interface. The controller may then generate a signal for applying compensation to the differential inputs to reduce or eliminate the undesired effects.

One method of processing microphone input in an ADC to determine microphone configuration is to process the microphone input signals in two processing paths, in which one processing path processes a difference between differential input signals and another processing path processes an average value of the differential input signals. The outputs of these processing paths may be combined to generate a digital signal representative of the analog signal from the microphone. The digital signal contains a digital version of the audio in the environment around the microphone, but may also be used to detect microphone topology and configure aspects of the processing paths to match the detected microphone topology. An apparatus for an ADC may implement the two processing paths as two delta-sigma modulator loops.

Described examples include multistage amplifier circuits having first and second forward circuits, a comparator or sensor circuit coupled to sense a signal in the second forward circuit to identify nonlinear operation or slewing conditions in the multistage amplifier circuit, and one or more sample hold circuits operative according to a sensor circuit output signal to selectively maintain the amplitude of an amplifier input signal in the second forward circuit and/or in a feedback circuit in response to the sensor circuit output signal indicating nonlinear operation or slewing conditions in the multistage amplifier circuit. Certain examples further include a clamping circuit operative to selectively maintain a voltage at a terminal of a Miller compensation capacitance responsive to the comparator output signal indicating nonlinear operation or slewing conditions.

Described examples include multistage amplifier circuits having first and second forward circuits, a comparator or sensor circuit coupled to sense a signal in the second forward circuit to identify nonlinear operation or slewing conditions in the multistage amplifier circuit, and one or more sample hold circuits operative according to a sensor circuit output signal to selectively maintain the amplitude of an amplifier input signal in the second forward circuit and/or in a feedback circuit in response to the sensor circuit output signal indicating nonlinear operation or slewing conditions in the multistage amplifier circuit. Certain examples further include a clamping circuit operative to selectively maintain a voltage at a terminal of a Miller compensation capacitance responsive to the comparator output signal indicating nonlinear operation or slewing conditions.

One method of processing microphone input in an ADC to determine microphone configuration is to process the microphone input signals in two processing paths, in which one processing path processes a difference between differential input signals and another processing path processes an average value of the differential input signals. The outputs of these processing paths may be combined to generate a digital signal representative of the analog signal from the microphone. The digital signal contains a digital version of the audio in the environment around the microphone, but may also be used to detect microphone topology and configure aspects of the processing paths to match the detected microphone topology. An apparatus for an ADC may implement the two processing paths as two delta-sigma modulator loops.

An analog-to-digital converter (ADC) may include capability to sense and/or compensate for undesired effects when receiving input from a microphone. For example, a sense node may be provided between differential inputs, and that sense node separated from the differential inputs by two or more switches. The sense node may allow for a measurement of an average voltage of the differential inputs. The average voltage may be obtained activating the switches to sample the sampling capacitors coupled to the differential inputs. That average voltage may be used as common mode (CM) data. A controller may receive the CM data, along with differential mode (DM) data, and use the CM and DM data to determine undesired effects, such as DC or AC mismatch at the microphone interface. The controller may then generate a signal for applying compensation to the differential inputs to reduce or eliminate the undesired effects.

A microphone preamplifier circuit is adapted to be connected to a microphone circuit, the microphone circuit including a microphone and at least one output node. The microphone preamplifier circuit includes a preamplifier including: an operational amplifier having at least one input and at least one output; at least one input DC decoupling capacitor connected to the at least one input of the operational amplifier; at least one feedback capacitor connected between the input and the output of the operational amplifier in order to set together with the at least one input DC decoupling capacitor a gain value of the preamplifier circuit; and first and second feed nodes adapted to be fed by first and second bias voltages respectively. The preamplifier further includes at least one switched capacitor adapted to be selectively and alternatively connected in response to a clock signal: between the at least one input and the at least one output of the operational amplifier; and between the first and second feed nodes. The microphone preamplifier circuit further includes an anti-aliasing filter having: (i) at least one output terminal connected to the at least one input DC decoupling capacitor and (ii) at least one input terminal adapted to be connected to the at least one output node of the microphone circuit.