Abstract: A single photon avalanche diode (SPAD) pixel circuit includes a SPAD, a clamping transistor coupled to the anode of the SPAD, and readout circuitry. The clamping transistor limits the anode voltage to a threshold below the readout circuitry's maximum operating voltage. In one embodiment, quenching and enabling transistors are implemented using single-layer gate oxide technology, while the clamping transistor uses extended drain technology. A regulation circuit generates a voltage clamp control signal for an array of pixels. Another embodiment utilizes a stacked chip design with the SPAD and a cathode-side quenching element on one chip, and the clamping transistor and readout circuitry on another. This incorporates a parasitic capacitance from deep trench isolation. Additional biasing transistors may be used for fine-tuning the clamped anode voltage.

Abstract: The present disclosure relates to an avalanche photodiode pixel including: a transistor adapted to be controlled by an enable signal having a first state for controlling the enabling of the pixel and a second state for controlling the disabling of the pixel, the transistor being configured to couple an avalanche photodiode of the pixel to a node of application of a substrate voltage when the enable signal is in the first state; and an output circuit adapted to be controlled by the enable signal and configured to provide a pixel output signal when the enable signal is in the first state and to block the pixel output signal when the enable signal is in the second state.

Abstract: Disclosed herein is an array of pixels. Each pixel includes a single photon avalanche diode (SPAD) and a transistor circuit. The transistor circuit includes a clamp transistor configured to clamp an anode voltage of the SPAD to be no more than a threshold clamped anode voltage, and a quenching element in series with the clamp transistor and configured to quench the anode voltage of the SPAD when the SPAD is struck by an incoming photon. Readout circuitry is coupled to receive the clamped anode voltage from the transistor circuit and to generate a pixel output therefrom, the threshold clamped anode voltage being below a maximum voltage rating of transistors forming the readout circuitry.

Abstract: A pixel includes a SPAD having a cathode connected to a first node and an anode coupled to a first negative voltage, and a transistor circuit coupled between a supply voltage and a third node, that turns on in response to an enable signal. A cascode transistor connected between the third node and the first node is controlled by a cascode control signal. A cathode setting capacitor is connected between the first node and ground. A readout inverter is coupled between the intermediate node and an output node and generates an output signal. Turn-on of the transistor circuit sources current from the supply voltage node to the cathode setting capacitor, setting a reverse bias voltage across the SPAD to greater than its breakdown voltage. A photon impinging upon the SPAD cause avalanche of the SPAD which, when occurring after turn off of the transistor circuit, discharges the cathode setting capacitor.

Abstract: An array of single photon avalanche diodes (SPADs) includes a plurality of pixels. Each pixel includes a SPAD having a cathode connected to a first intermediate node and an anode coupled to first negative voltage, a quench circuit connected between the first intermediate node and the low voltage supply node, an AC coupling element connected between the first intermediate node and a second intermediate node, a filter component connected between the high voltage node and the second intermediate node, and an inverter having its input connected to the second intermediate node and its output providing an output signal. A resistance associated with the quench circuit, a capacitance associated with the SPAD, a capacitance associated with the AC coupling element, and a resistance associated with the filter component form a variable second order filter.

Abstract: Disclosed herein is a single photon avalanche diode (SPAD) pixel for use in time-of-flight imaging. This pixel includes a SPAD having a cathode connected to a first node and an anode coupled to first negative voltage. A transistor circuit in the pixel includes a quench transistor connected between a supply voltage node and a second node, the quench transistor controlled by a quench control signal to operate in a high-impedance mode, and a recharge transistor connected in parallel with the quench transistor between the supply voltage node and the second node, the recharge transistor controlled by a feedback signal. The pixel also includes a readout inverter generating an output signal based upon a voltage at the first node and an adjustable delay circuit generating the feedback signal based upon the output signal, the feedback signal being delayed with respect to the output signal.

Abstract: A CMOS-based chip having multiple sensing modalities that are able independently to detect multiple metabolites present in a sample. In particular, the chip provides multiple sensing modalities capable of performing detection within the same physical test volume, i.e. the chip can simultaneously detect a plurality of chemical reactions occurring in the test volume, where each chemical reaction yields a result that is independently detectable. The chip may comprise an optical sensor (e.g. photodiode) and a chemical sensor (e.g. pH sensor, embodied as an ISFET). With this technique, multiple metabolites may be measured in real time using a small scale point-of-care device.

Abstract: A CMOS-based chip having one or more sensing modalities that are able independently to detect multiple metabolites present in a biological sample. The multiple sensing modalities may be provided at different locations with respect to the chip, whereby the chip can simultaneously detect a plurality of metabolites by measuring behaviour of a test material in the different locations. The chip may utilise paper as a transport mechanism for the sample. The paper either conveys the sample to the different locations or itself provides discrete testing zones in which different metabolites can be independently detected. With this technique, multiple metabolites may be measured in real time using a small scale point-of-care device.

Abstract: A single photon avalanche diode (SPAD) has a cathode coupled to a high voltage supply and an anode coupled to a first node. A photodetection circuit includes: a first n-channel transistor having a drain coupled to the first node, a source coupled to ground, and a gate coupled to a third node; a second n-channel transistor having a drain coupled to the first node, a source coupled to ground, and a gate coupled to a second node; and an inverter having an input coupled to the first node and an output coupled to an intermediate node. A current starved inverter has an input coupled to the intermediate node and an output coupled to the second node, a logic gate has inputs coupled to the intermediate node and the second node, and an output coupled to the third node.

Abstract: Disclosed herein is an array of pixels. Each pixel includes a single photon avalanche diode (SPAD) and a transistor circuit. The transistor circuit includes a clamp transistor configured to clamp an anode voltage of the SPAD to be no more than a threshold clamped anode voltage, and a quenching element in series with the clamp transistor and configured to quench the anode voltage of the SPAD when the SPAD is struck by an incoming photon. Readout circuitry is coupled to receive the clamped anode voltage from the transistor circuit and to generate a pixel output therefrom, the threshold clamped anode voltage being below a maximum voltage rating of transistors forming the readout circuitry.

Abstract: A pixel includes a single photon avalanche diode (SPAD) having a cathode coupled to a high voltage supply through a quenching element, with the SPAD having a capacitance at its anode formed from a deep trench isolation, with the quenching element having a sufficiently high resistance such that the capacitance is not fully charged when the SPAD is struck by an incoming photon. The pixel includes a clamp transistor configured to be controlled by a voltage clamp control signal to clamp voltage at an anode of the SPAD when the SPAD is struck by an incoming photon to be no more than a threshold clamped anode voltage, and readout circuitry coupled to receive the clamped anode voltage from the clamp transistor and to generate a pixel output therefrom. The threshold clamped anode voltage is below a maximum operating voltage rating of transistors forming the readout circuitry.

Abstract: A single photon avalanche diode (SPAD) has a cathode coupled to a high voltage supply and an anode coupled to a first node. A photodetection circuit includes: a first n-channel transistor having a drain coupled to the first node, a source coupled to ground, and a gate coupled to a third node; a second n-channel transistor having a drain coupled to the first node, a source coupled to ground, and a gate coupled to a second node; and an inverter having an input coupled to the first node and an output coupled to an intermediate node. A current starved inverter has an input coupled to the intermediate node and an output coupled to the second node, a logic gate has inputs coupled to the intermediate node and the second node, and an output coupled to the third node.

Abstract: A photodetection circuit includes a single photon avalanche diode (SPAD) having a cathode coupled to a high voltage supply through a quench resistance and an anode coupled to a first node, a capacitive deep trench isolation capacitor coupled between the first node and ground, and a first n-channel transistor. The first n-channel transistor has a drain coupled to the first node, a source coupled to ground, and a gate coupled to a resistance control signal. A second n-channel transistor has a drain coupled to the first node, a source coupled to ground, and a gate coupled to a second node. An inverter has an input coupled to the first node and an output coupled to an intermediate node. A current starved inverter has an input coupled to the intermediate node and an output coupled to the second node.

Abstract: A photodetection circuit includes a single photon avalanche diode (SPAD), and an active quenching circuit coupling the SPAD to an intermediate node and having a variable RC constant. The variable RC constant provides a first RC constant during an idle state so that when the SPAD detects a photon, the SPAD avalanches to begin quenching to set a magnitude of a voltage at a terminal of the SPAD to a quench voltage, the quench voltage being greater than a threshold voltage; a second RC constant greater than the first RC constant during a hold off period during which the quenching occurs so as to maintain the voltage at the terminal of the SPAD at a magnitude that is above the threshold voltage during the hold off period; and a third RC constant less than the second RC constant but greater than the first RC constant during a recharge period during which the SPAD is recharged.

Abstract: A pixel includes a single photon avalanche diode (SPAD) having a cathode coupled to a high voltage supply through a quenching element, with the SPAD having a capacitance at its anode formed from a deep trench isolation, with the quenching element having a sufficiently high resistance such that the capacitance is not fully charged when the SPAD is struck by an incoming photon. The pixel includes a clamp transistor configured to be controlled by a voltage clamp control signal to clamp voltage at an anode of the SPAD when the SPAD is struck by an incoming photon to be no more than a threshold clamped anode voltage, and readout circuitry coupled to receive the clamped anode voltage from the clamp transistor and to generate a pixel output therefrom. The threshold clamped anode voltage is below a maximum operating voltage rating of transistors forming the readout circuitry.

Abstract: A photodetection circuit includes a single photon avalanche diode (SPAD) having a cathode coupled to a high voltage supply through a quench resistance and an anode coupled to a first node, a capacitive deep trench isolation capacitor coupled between the first node and ground, and a first n-channel transistor. The first n-channel transistor has a drain coupled to the first node, a source coupled to ground, and a gate coupled to a resistance control signal. A second n-channel transistor has a drain coupled to the first node, a source coupled to ground, and a gate coupled to a second node. An inverter has an input coupled to the first node and an output coupled to an intermediate node. A current starved inverter has an input coupled to the intermediate node and an output coupled to the second node.

Abstract: A photodetection circuit includes a single photon avalanche diode (SPAD), and an active quenching circuit coupling the SPAD to an intermediate node and having a variable RC constant. The variable RC constant provides a first RC constant during an idle state so that when the SPAD detects a photon, the SPAD avalanches to begin quenching to set a magnitude of a voltage at a terminal of the SPAD to a quench voltage, the quench voltage being greater than a threshold voltage; a second RC constant greater than the first RC constant during a hold off period during which the quenching occurs so as to maintain the voltage at the terminal of the SPAD at a magnitude that is above the threshold voltage during the hold off period; and a third RC constant less than the second RC constant but greater than the first RC constant during a recharge period during which the SPAD is recharged.

Abstract: A CMOS-based chip having one or more sensing modalities that are able independently to detect multiple metabolites present in a biological sample. The multiple sensing modalities may be provided at different locations with respect to the chip, whereby the chip can simultaneously detect a plurality of metabolites by measuring behaviour of a test material in the different locations. The chip may utilise paper as a transport mechanism for the sample. The paper either conveys the sample to the different locations or itself provides discrete testing zones in which different metabolites can be independently detected. With this technique, multiple metabolites may be measured in real time using a small scale point-of-care device.

Abstract: A CMOS-based chip having multiple sensing modalities that are able independently to detect multiple metabolites present in a sample. In particular, the chip provides multiple sensing modalities capable of performing detection within the same physical test volume, i.e. the chip can simultaneously detect a plurality of chemical reactions occurring in the test volume, where each chemical reaction yields a result that is independently detectable. The chip may comprise an optical sensor (e.g. photodiode) and a chemical sensor (e.g. pH sensor, embodied as an ISFET). With this technique, multiple metabolites may be measured in real time using a small scale point-of-care device.