Improved dither detection, measurement, and voltage bias adjustments for an electro-optical modulator are described. The electro-optical modulator generally includes RF electrodes and phase heaters interfaced with semi-conductor waveguides on the arms of Mach-Zehnder interferometers, where a processor is connected to output a bias tuning voltage to the electro-optical modulator for controlling optical modulation. A variable gain amplifier (VGA) can be configured with AC coupling connected to receive a signal from a transimpediance amplifier (TIA) that is configured to amply a photodetector signal from an optical tap that is used to measure an optical signal with a dither signal. The analog to digital converter (ADC) can be connected to receive output from the VGA. The processor can be connected to receive the signal from the ADC and to output the bias tuning voltage based on evaluation of the signal from the tap.

Amplifier devices includes a first amplifier connected to receive an input voltage. The first amplifier outputs an internal voltage. These structures also include a second amplifier having an input node connected to receive the internal voltage and an output node outputting an output voltage. A resistive feedback loop is connected to the input node and the output node of the second amplifier. A first cross-coupled bandwidth boosting stage is connected to the input node of the second amplifier and a second cross-coupled bandwidth boosting stage connected to the output node of the second amplifier. The cross-coupled bandwidth boosting stages form a distributed differential positive feedback structure.

A transimpedance amplifier (TIA) device. The device includes a photodiode coupled to a differential TIA with a first and second TIA, which is followed by a Level Shifting/Differential Amplifier (LS/DA). The photodiode is coupled between a first and a second input terminal of the first and second TIAs, respectively. The LS/DA can be coupled to a first and second output terminal of the first and second TIAs, respectively. The TIA device includes a semiconductor substrate comprising a plurality of CMOS cells, which can be configured using 28 nm process technology to the first and second TIAs. Each of the CMOS cells can include a deep n-type well region. The second TIA can be configured using a plurality CMOS cells such that the second input terminal is operable at any positive voltage level with respect to an applied voltage to a deep n-well for each of the plurality of second CMOS cells.

An amplification interface includes first and second differential input terminals, first and second differential output terminals providing first and second output voltages defining a differential output signal, and first and second analog integrators coupled between the first and second differential input terminals and the first and second differential output terminals, the first and second analog integrators being resettable by a reset signal. A control circuit generates the reset signal such that the first and second analog integrators are periodically reset during a reset interval and activated during a measurement interval, receives a control signal indicative of offsets in the measurement sensor current and the reference sensor current, and generates a drive signal as a function of the control signal. First and second current generators coupled first and second compensation circuits to the first and second differential input terminals as a function of a drive signal.

A transimpedance amplifier (TIA) for converting an input current at an input node into an output voltage at an output node, the TIA comprising: a first amplifier stage having a first input coupled to the input node and a first output; a feedback path between the first output and the first input; a second amplifier stage in the feedback path having a second input, the second input coupled to the first output of the first amplifier stage; a feedback resistor in the feedback path coupled between an output of the second amplifier stage and first input of the first amplifier stage; and an output stage, comprising: a load resistor coupled between a reference voltage node and a T-coil, the T-coil comprising first and second inductors coupled in series at an inductor node, the T-coil coupled between the first output and the load resistor, the inductor node coupled to the output node of the TIA.

A surface plasmon-based photodetector includes: a silicon substrate; a grating in contact with a surface of the silicon substrate, in which the grating forms a Schottky diode with the semiconductor substrate; and a complementary-metal-oxide-semiconductor (CMOS) sample and hold stage as well as an analog-to-digital circuit (ADC) in the silicon substrate and arranged to detect electrical current generated at the Schottky diode.

Mechanisms for evaluating amplitude for current pulses provided to a transimpedance amplifier (TIA) for current levels beyond the linear range of the TIA where clipping circuit(s) may limit the input voltage of the TIA are disclosed. In one aspect, an example TIA arrangement includes a clipping arrangement that includes multiple clipping circuits. Each clipping circuit can be biased by different bias voltages such that the different clipping circuits are activated at different input current amplitudes. Different clipping circuits can have different impedances, which can result in different recovery time characteristics. With the multiple clipping circuits in clipping arrangements discussed herein, a saturated dynamic range of a TIA can be divided into sub-regions and different pulse widening characteristics for each region may be defined, which may enable determination of amplitude for current pulses provided to the TIA even for current levels beyond the linear range of the TIA.

A sensor is provided. A first terminal of a first current source and a first terminal of a first transistor are connected to a cathode of the photodiode. A control terminal of a second transistor is connected to an output terminal of a first operational amplifier. A first terminal of the second transistor is connected to a second terminal of the first transistor through a first current mirror circuit. A second terminal of the second transistor is connected to a second current source, a second input terminal of a second operational amplifier and a first terminal of a third transistor. A first input terminal of the second operational amplifier is connected to the first terminal of the first transistor. A control terminal of the third transistor is connected to an output terminal of the second operational amplifier.

Low-noise optical differential receivers are described. Such differential receivers may include a differential amplifier having first and second inputs and first and second outputs, and four photodetectors. A first and a second of such photodetectors are coupled to the first input of the differential amplifier, and a third and a fourth of such photodetectors are coupled to the second input of the differential amplifier. The anode of the first photodetector and the cathode of the second photodetector are coupled to the first input of the differential amplifier. The cathode of the third photodetector and the anode of the fourth photodetector are coupled to the second input of the differential amplifier. The optical receiver may involve two stages of signal subtraction, which may significantly increase noise immunity.

A control device may comprise a passive infrared sensing circuit configured to operate in a charging state to charge one or more capacitors to appropriate voltages for operation in an operational state of the sensing circuit. The sensing circuit may comprise a pyroelectric detector configured to generate an output signal in response to received infrared energy, and first and second amplifier circuits configured to amplify the output signal. The control device may comprise a control circuit coupled to receive a sensing signal from the second amplifier circuit. Prior to the operational state, a capacitor of the first amplifier circuit may charge through a diode coupled between an output and an inverting input of an operational amplifier. In addition, prior to the operational state, a capacitor of the passive infrared sensing circuit may charge through the control circuit until the magnitude of a voltage across the capacitor exceeds a threshold voltage.