AC Mode operation of chemfet devices

• US 4,488,556 A
• Filed: 06/03/1982
• Issued: 12/18/1984
• Est. Priority Date: 06/03/1982
• Status: Expired due to Term

• Current Assignee: Critikon Co. LLC
• Original Assignee: Critikon, Inc.
• Inventors: Ho, Nelson
• Primary Examiner(s): Kaplan, G. L.
• Application Number:
  US06/384,710
• Time in Patent Office: 929 Days
• Field of Search: 204/406, 204/416, 357/25, 324/71.5, 324/71.6, 128/635
• US Class Current: 600/348
• CPC Class Codes: G01N 27/4148 Integrated circuits therefor, e.g. fabricated by CMOS processing CMOS processing per se H01L21/82

Abstract

A chemically sensitive field effect device has its chemically selective system exposed to the material being investigated. The device is driven by a time varying, typically sinusoidal, current source. A protected reference electrode is also in contact with the body under investigation, and is biased at a predetermined DC level relative to the chemically sensitive field effect device.

Claims

1. In combination, a chemically sensitive field effect transducer apparatus, means for coupling a sinusoidal drain-source potential to said transducer, and means for maintaining the gate of said transducer at a DC potential equal to the combination of a bias potential plus an electrochemically generated potential by a substance being sensed.

2. Apparatus as described in claim 1 and further comprising a reference electrode maintained at a predetermined DC bias relatve to the source electrode.

3. Apparatus as described in claim 2 wherein said means for generating generates a waveform having a frequency in the range between 10 Hz. and 1 MHz.

4. Apparatus as described in claim 3 wherein said means for generating generates a waveform having a frequency in the range between 100 kHz. and 200 kHz.

5. Apparatus for sensing the presence of a specified substance in a subject comprising:

(a) a chemically sensitive field effect device having respective drain and source connections, a drain to source conduction path, and a chemically selective system overlying said path and modulating current therein in response to presence of said substance in said subject;

(b) a reference electrode coupled to said subject;

(c) means for generating and for coupling to said conduction path a sinusoidal time variant signal; and

(d) means, coupled between said source and said reference electrode, for establishing a gate potential consisting of a bias potential plus the potential generated electrochemically by said specified substance.

6. Apparatus as described in claim 5 wherein said means for generating comprises means for generating a substantially sinusoidal current waveform having a mean value of approximately zero volts.

7. Apparatus as described in claim 6 wherein said means for generating generates a waveform having a frequency in the range between 10 Hz. and 1 MHz.

8. Apparatus as described in claim 6 wherein said means for generating generates a waveform having a frequency in the range between 100 kHz. and 200 kHz.