Patent ID: 8742469

Claim:
An apparatus, comprising: an array of sensors, a sensor in the array including: a chemically-sensitive field effect transistor (chemFET) having a first conduction terminal, a second conduction terminal coupled to a first supply voltage conductor, and a sensor surface; a first transistor having a first conduction terminal coupled to the first conduction terminal of the chemFET, a second conduction terminal coupled to a second supply voltage conductor, and a gate coupled to a bias voltage conductor; and a second transistor having a gate coupled to a first control signal conductor, a first conduction terminal coupled to the first conduction terminal of the chemFET, and a second conduction terminal coupled to an amplifier node; a reset circuit coupled to the amplifier node and having an input coupled to a second control signal conductor, the reset circuit to reset the amplifier node to a reference voltage in response to a signal on the second control signal conductor; an amplifier having an input connected to the amplifier node and having an output coupled to an output conductor, the amplifier includes: a third transistor having a gate coupled to the amplifier node, a first conduction terminal coupled to a third supply voltage conductor, and a second conduction terminal; and a fourth transistor having a gate coupled to a select signal conductor, a first conduction terminal coupled to the second conduction terminal of the third transistor, and a second conduction terminal coupled to the output conductor; and a controller to cause the amplifier to provide a first output while the amplifier node is reset to the reference voltage, and to cause the amplifier to provide a second output while the chemFET is coupled to the amplifier node.