AMPLIFIER AND ARRAY FOR MEASURING SMALL CURRENT

• US 20110121819A1
• Filed: 11/25/2008
• Published: 05/26/2011
• Est. Priority Date: 11/29/2007
• Status: Active Grant

• Current Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Original Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Inventors: Ayers, Sunitha Bandla, Lindau, Manfred, Minch, Bradley A.
• Granted Patent: US 9,086,400 B2
• Time in Patent Office: Days
• US Class Current: 324/123.C
• CPC Class Codes: G01N 15/10 Investigating individual particles
• CPC Class Codes: G01N 27/403 Cells and electrode assemblies
• CPC Class Codes: G01N 27/49 Systems involving the determination of the current at a single specific value, or small range of values, of applied voltage for producing selective measurement of one or more particular ionic species
• CPC Class Codes: G01N 33/487 of liquid biological material
• CPC Class Codes: G01N 33/48728 Investigating individual cells, e.g. by patch clamp, voltage clamp investigating individual particles in general G01N15/10

Abstract

An array of electrochemical detectors includes an array of electrodes that provide current responsive to oxidation events. Each electrode is coupled to a transistor, an amplifier coupled to an input of the transistor and having a feedback loop coupled to the electrode and providing a bias voltage to the electrode, an integrating capacitor coupled to the transistor operable to integrate charge from the electrode, and a reset switch coupled to the integrating capacitor. The amplifier may have a shared stage with other detectors. A shared buffer circuit may also provide a sampled output from multiple detectors.

Claims

1. A device comprising:

a substrate;

an array of electrodes supported by the substrate;

circuitry supported by the substrate and integrated with the array of electrodes adapted to measure transient amperometric oxidation currents from the electrodes.

2. The device of claim 1 wherein the circuitry comprises an amplifier and an integrating capacitor for each electrode in the array.

3. The device of claim 2 wherein the amplifier has a feedback loop to bias each electrode at a desired reference voltage.

4. The device of claim 2 wherein the integrating capacitor further comprises a switch for draining charge from the capacitor at desired times.

5. The device of claim 1 wherein the circuitry comprises multiple amplifiers formed with a shared half circuit, and the non-shared half of each amplifier being associated with each electrode.

6. The device of claim 5 wherein the shared half circuit comprises a non-inverting half of the amplifiers is a folded cascode amplifier adapted to provide a large output voltage swing and provide a low input impedance.

7. The device of claim 5 wherein the non-shared half of each amplifier is a folded cascode amplifier having a voltage output that is substantially rail to rail.

8. The device of claim 1 wherein the circuitry comprises a current to voltage converter.

9. The device of claim 8 wherein the current to voltage converter is integrating or non-integrating.

10. The device of claim 1 wherein the array comprises at least 25 amplifiers and 25 electrodes.

11. A device for measuring current, the device comprising:

a cascode transistor for coupling to an input electrode;

an amplifier coupled to an input of the cascode transistor and having a feedback loop for coupling to the electrode and providing a bias voltage to the electrode;

an integrating capacitor coupled to the cascode transistor for integrating charge from the input electrode; and

a reset switch coupled to the integrating capacitor.

12. The device of claim 11 wherein the device is formed on a single chip having an opening for the input electrode.

13. The device of claim 11 wherein the amplifier comprises a split amplifier sharing an input stage with other devices.

14. The device of claim 13 wherein the shared input stage comprises a non-inverting stage of the amplifier and includes an error amplifier.

15. An array of electrochemical detectors comprising:

an array of electrodes that provides current responsive to oxidation events, each electrode coupled to;

a transistor;

an amplifier coupled to an input of the transistor and having a feedback loop coupled to the electrode and providing a bias voltage to the electrode;

an integrating capacitor coupled to the transistor operable to integrate charge from the electrode; and

a reset switch coupled to the integrating capacitor.

16. The array of claim 15 wherein multiple electrodes share a first half of the amplifier.

17. The array of claim 16 wherein electrodes in a row of the array share the first half of the amplifier.

18. The array of claim 16 wherein the first half of the amplifier is a non-inverting half of the amplifier.

19. The array of claim 16 wherein each electrode has a dedicated second, inverting half of the amplifier.

20. The array of claim 19 wherein the inverting half of the amplifier comprises a folded cascode set of transistors and a load transistor such that a substantially rail to rail output is provided by the inverting half of the amplifier.

21. The array of claim 15 wherein the amplifier comprises equivalent thermal noise current sources.

22. The array of claim 15 wherein the amplifier comprises a regulated cascode amplifier.

23. A shared amplifier array comprising:

a first shared non-inverting amplifier stage coupled to a reference voltage;

multiple second inverting amplifier stages sharing the first shared non-inverting amplifier stage, the inverting amplifier stages formed in a folded cascode arrangement such that it provides a substantially rail to rail output voltage.

24. The shared amplifier array of claim 23 wherein the first non-inverting amplifier stage comprises a feedback loop to lower an input impedance.

25. The shared amplifier array of claim 24 wherein the feedback loop comprises two transistors.

26. The shared amplifier array of claim 23 wherein the first non-inverting amplifier stage comprises an error amplifier.

27. A current detector array comprising:

a plurality of detectors, each having an electrode for providing current from oxidation events, an amplifier for biasing the electrodes, a cascode transistor, and an integrating capacitor;

a shared buffer circuit; and

a switch coupled to each detector for alternately switching each of the detectors to the shared buffer circuit.

28. A method comprising:

distributing multiple small current producing entities across a substrate having an array of electrodes supported by the substrate and circuitry supported by the substrate and integrated with the array of electrodes adapted to measure transient amperometric oxidation currents from the electrodes; and

measuring current produced by the current producing entities at each electrode in the array of electrodes.