ARRAY COLUMN INTEGRATOR

• US 20120001615A1
• Filed: 06/30/2011
• Published: 01/05/2012
• Est. Priority Date: 06/30/2010
• Status: Active Grant

• Current Assignee: Life Technologies Corporation (Thermo Fisher Scientific Incorporated)
• Original Assignee: Life Technologies Corporation (Thermo Fisher Scientific Incorporated)
• Inventors: LEVINE, Peter
• Granted Patent: US 8,432,149 B2
• Time in Patent Office: Days
• US Class Current: 324/71.5
• CPC Class Codes: C12Q 1/6869 Methods for sequencing
• CPC Class Codes: G01J 1/46 using a capacitor
• CPC Class Codes: G01N 27/4143 Air gap between gate and channel, i.e. suspended gate [SG] FETs work function measurement per se G01N27/002
• CPC Class Codes: G01N 27/4145 specially adapted for biomolecules, e.g. gate electrode with immobilised receptors
• CPC Class Codes: G01N 27/4148 Integrated circuits therefor, e.g. fabricated by CMOS processing CMOS processing per se H01L21/82
• CPC Class Codes: G01N 33/00 Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
• CPC Class Codes: G01R 29/26 Measuring noise figure; Measuring signal-to-noise ratio
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H01L 27/14632 Wafer-level processed structures
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 29/66 Types of semiconductor device ; Multistep manufacturing processes therefor
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: Y10T 436/25875 Gaseous sample or with change of physical state

Abstract

The described embodiments may provide a chemical detection circuit with an improved signal-to-noise ration. The chemical detection circuit may include a current source, a chemical detection pixel, an amplifier and a capacitor. The chemical detection pixel may comprise a chemical-sensitive transistor that may have a first and second terminals and a row-select switch coupled between the current source and chemically-sensitive transistor. The amplifier may have a first input and a second input, with the first input coupled to an output of the chemically-sensitive transistor via a switch and the second input coupled to an offset voltage line. The capacitor may be coupled between an output of the amplifier and the first input of the amplifier. The capacitor and amplifier may form an integrator and may be shared by a column of chemical detection pixels.

Claims

1. A chemical detection circuit, comprising:

a current source;

a chemical detection pixel, comprising;

a chemically-sensitive transistor having first and second terminals; and

a row-select switch coupled between the current source and one of said first and second terminals of said chemically-sensitive transistor;

an amplifier having a first input and a second input, the first input coupled to an output of the chemically-sensitive transistor via a switch and the second input coupled to an offset voltage line; and

a capacitor coupled between an output of the amplifier and the first input of the amplifier.

2. The chemical detection circuit of claim 1, wherein the chemically-sensitive transistor is an ion-sensitive field effect transistor (ISFET).

3. The chemical detection circuit of claim 1, wherein the chemically-sensitive pixel is one of a column of chemically-sensitive pixels.

4. The chemical detection circuit of claim 1, wherein the chemically-sensitive transistor works in a current-mode during operation, and the switch between the first input of the amplifier and one of the first and second terminals of the chemical-sensitive transistor is a select switch.

5. The chemical detection circuit of claim 4, wherein the current source is a programmable current source.

6. The chemical detection circuit of claim 1, further comprising a resistor coupled to the first input of the amplifier, wherein the chemical-sensitive transistor works in a voltage-mode during operation, and the switch between the first input of the amplifier and the output of the chemically-sensitive transistor is an output switch, the resistor is placed between the output switch and the first input of the amplifier, and the voltage output of the chemically-sensitive transistor is converted to current by the offset voltage setting an appropriate voltage for the first input of the amplifier.

7. The chemical detection circuit of claim 6, wherein the resistor is a pass transistor with a gate voltage provided by a process, voltage and temperature (PVT) independent bias circuit.

8. The chemical detection circuit of claim 1, further comprising an analog-to-digital converter (ADC) coupled to the output of the amplifier.

9. The chemical detection circuit of claim 1, further comprising a first switch coupled between the first input of the amplifier and the output of the amplifier, a second switch coupled between the capacitor and the output of the amplifier and a third switch coupled between the capacitor and ground, wherein during operation:

in an integration phase, the first and third switches are left open and the second switch is closed to let a readout current from the chemical detection pixel to integrate onto the capacitor; and

in a clear phase, the first and third switches are closed and the second switch is left open to clear electrical charges accumulated on the capacitor.

10. A chemical detection circuit, comprising:

a plurality of columns of chemical detection pixels, each column comprising

a current source;

a plurality of chemical detection pixels, each chemical detection pixel comprising;

a chemical-sensitive transistor having first and second terminals; and

a row-select switch coupled between the current source and chemically-sensitive transistor;

an amplifier having a first input and a second input, the first input coupled to an output of each of the chemically-sensitive transistors via a respective switch and the second input coupled to an offset voltage line; and

a capacitor coupled between an output of the amplifier and the first input of the amplifier.

11. The chemical detection circuit of claim 10, wherein each chemically-sensitive transistor is an ion-sensitive field effect transistor (ISFET).

12. The chemical detection circuit of claim 10, wherein each chemically-sensitive transistor is to work in a current-mode during operation, the respective switch between the first input of the amplifier and the output of the chemical-sensitive transistor is a respective row-select switch.

13. The chemical detection circuit of claim 12, wherein the current source is a programmable current source.

14. The chemical detection circuit of claim 10, further comprising a resistor coupled to the first input of the amplifier, wherein each chemically-sensitive transistor is to work in a voltage-mode during operation, the respective switch between the first input of the amplifier and each output of the chemical-sensitive transistor is a respective output switch for each chemical detection pixel, the resistor is placed between the respective output switches and the first input of the amplifier, and the voltage output of each chemically-sensitive transistor is converted to current by the offset voltage setting an appropriate voltage for the first input of the amplifier.

15. The chemical detection circuit of claim 14, wherein the resistor is a pass transistor with a gate voltage provided by a process, voltage and temperature (PVT) independent bias circuit.

16. The chemical detection circuit of claim 10, further comprising an analog-to-digital converter (ADC) coupled to the output of the amplifier.

17. The chemical detection circuit of claim 10, further comprising a first switch coupled between the first input of the amplifier and the output of the amplifier, a second switch coupled between the capacitor and the output of the amplifier and a third switch coupled between the capacitor and ground, wherein during operation:

in an integration phase, the first and third switches are left open and the second switch is closed to let a readout current from the chemical detection pixel to integrate onto the capacitor; and

in a clear phase, the first and third switches are closed and the second switch is left open to clear electrical charges accumulated on the capacitor.

18. A method to generate an output signal from a chemical detection circuit, comprising:

selecting a chemical detection pixel from a column of chemical detection pixels for readout;

integrating a readout current from the chemical detection pixel to an integrator; and

reading out an output voltage of the integrator.

19. The method of claim 18, wherein the readout current is caused by a voltage change at a gate terminal of the selected chemical detection pixel.

20. The method of claim 19, wherein the selected chemical detection pixel works in a current mode and a change of ion concentration at a gate terminal of the selected chemical detection pixel generates the read current to be supplied to a capacitor of the integrator.

21. The method of claim 19, wherein the selected chemical detection pixel works in a voltage mode and a change of ion concentration at a gate terminal of the selected chemical detection pixel generates an output voltage, the output voltage is applied over a resistor to generate the readout current to be supplied to a capacitor of the integrator.

22. The method of claim 18, further comprising clearing electrical charges accumulated on a capacitor of the integrator.

23. The method of claim 18, further comprising performing a correlated-double-sampling (CDS) to store an inherent offset voltage to the integrator.