Patent ID: 8858782

Claim:
An ion-sensitive circuit, comprising: a charge-accumulation device to accumulate a plurality of charge packets as a function of an ion concentration of a fluid, including: a substrate having formed thereon a gate oxide layer; a first charge control electrode, formed over a first electrode semiconductor region and disposed on the gate oxide layer, to control entry of charge from the ion concentration of the fluid into a gate semiconductor region in response to a first control signal applied to the first electrode; an electrically floating gate structure disposed between a gate semiconductor region and an ion-sensitive passivation surface configured to receive the fluid, the floating gate includes a plurality of conductors electrically coupled to one another and separated by dielectric layers; and a second charge control electrode, formed over a second electrode semiconductor region and disposed on the gate oxide layer, to control transmission of the plurality of charge packets out of the gate semiconductor region and into a drain diffusion region in response to a second control signal applied to the second electrode; and a drain diffusion region to receive the plurality of charge packets from the gate semiconductor region via the second electrode semiconductor region, at least one control and readout transistor to generate an output voltage as a function of the accumulated plurality of charge packets at the drain diffusion region of the charge accumulation device, wherein the output voltage is representative of the ion concentration of the solution.