Integrated sensor arrays for biological and chemical analysis
View Patent ↗An apparatus comprising a chemical field effect transistor array in a circuit-supporting substrate is disclosed. The transistor array has disposed on its surface an array of sample-retaining regions capable of retaining a chemical or biological sample from a sample fluid. The transistor array has a pitch of 10 μm or less and a sample-retaining region is positioned on at least one chemical field effect transistor which is configured to generate at least one output signal related to a characteristic of a chemical or biological sample in such sample-retaining region.
1. An apparatus comprising:
a chemical field effect transistor array in a circuit-supporting substrate, such transistor array having disposed on its surface an array of sample-retaining regions capable of retaining a chemical or biological sample from a sample fluid, wherein such transistor array has a pitch of 10 μm or less and each sample-retaining region is positioned on at least one chemical field effect transistor which is configured to generate at least one output signal related to a characteristic of a chemical or biological sample in such sample-retaining region, the at least one chemical field effect transistor generating the at least one output signal at a circuit node at a first time interval, a first switch between the chemical field effect transistor and the circuit node to couple a terminal of the chemical field effect transistor to the circuit node in response to a select signal;
a reference circuit including a second switch directly connected to the circuit node for coupling a reference signal to the circuit node in response to a timing signal during a second time interval; and
a sampling circuit producing an output signal as a function of a first sample obtained during the first time interval and a second sample obtained during the second time interval.
2. The apparatus of claim 1 , wherein the output signal indicates a characteristic of a reaction involving the biological sample.
3. The apparatus of claim 2 , wherein the characteristic of the reaction is a concentration of a charged species in a sample fluid.
4. The apparatus of claim 3 , wherein the chemically-sensitive field effect transistor has a floating gate with a dielectric layer on a surface thereof.
5. The apparatus of claim 4 , wherein the dielectric layer comprises a metal oxide.
6. The apparatus of claim 5 , wherein the metal oxide is selected from the group consisting of aluminum oxide, tantalum oxide, silicon nitride, silicon oxynitride, tantalum pentoxide, tin oxide, and stannic oxide.
7. The apparatus of claim 1 , wherein the output signal is based on a difference between the first and the second samples.
8. The apparatus of claim 1 , wherein the sampling circuit includes a sample and hold capacitor, and a difference circuit that stores a difference between the first sample and the second sample on the sample and hold capacitor.
9. The apparatus of claim 1 , wherein the sampling circuit includes an amplifier having an input coupled to the circuit node and an output coupled by a switch to a sample and hold capacitor, and a feedback circuit between the input and output of the amplifier.
10. The apparatus of claim 9 , wherein the feedback circuit provides a first feedback path between the input and output of the amplifier during the first time interval, and provides a second feedback path between the input and output of the amplifier during the second time interval.
11. The apparatus of claim 10 , wherein: the first feedback path includes a first switch; and the second feedback path includes a feedback capacitor in series with a second switch.