Device for measuring a quantity which influences a field-effect transistor

• US 4,267,504 A
• Filed: 10/22/1979
• Issued: 05/12/1981
• Est. Priority Date: 11/06/1978
• Status: Expired due to Term

• Current Assignee: Philips Electronicsnorth America Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Bergveld, Piet
• Primary Examiner(s): Krawczewicz, Stanley T.
• Application Number:
  US06/086,922
• Time in Patent Office: 568 Days
• Field of Search: 324/62, 324/459, 324/464, 324/425, 324/431
• US Class Current: 324/721
• CPC Class Codes: G01N 27/4148 Integrated circuits therefor, e.g. fabricated by CMOS processing CMOS processing per se H01L21/82
• CPC Class Codes: G01R 17/00 Measuring arrangements involving comparison with a reference value, e.g. bridge
• CPC Class Codes: G01R 19/0023 Measuring currents or voltages from sources with high internal resistance by means of measuring circuits with high input impedance, e.g. OP-amplifiers electrostatic instruments G01R5/28; measuring electrostatic potential G01R15/165; measuring electrostatic fields G01R29/12; amplifiers per se H03F
• CPC Class Codes: G01R 19/32 Compensating for temperature change

Abstract

A device for measuring a quantity which influences a field-effect transistor which is included in a measuring circuit as a variable resistance. To compensate for temperature-dependent changes of the field-effect transistor, an auxiliary signal, having a frequency located outside the frequency range of the quantity to be measured, is applied to the transistor. The two signals are separated from one another again after having been processed by the measuring circuit.

Claims

1. A device for measuring a quantity comprising, a field-effect transistor having a source and a drain electrode, said field-effect transistor being located so as to be influenced by said quantity to be measured, means connecting said electrodes to terminals of a measuring circuit so that changes in the resistance between said electrodes influence the output voltage of the measuring circuit, means for applying to the field-effect transistor an auxiliary signal the frequency of which is located outside the frequency range in which changes of the quantity to be measured occur, and wherein the measuring circuit comprises means for separating signals at the frequency of the auxiliary signal from signals within the said frequency range.

2. A device as claimed in claim 1, characterized in that the quantity to be measured is applied to the field-effect transistor (1) via a first input and the auxiliary signal via a second input.

3. A device as claimed in claim 2, characterized in that the second input of the field-effect transistor comprises an electric connection which is connected to a substrate of said transistor.