Temperature sensor and method for operating a temperature sensor

• US 6,789,939 B2
• Filed: 08/13/2002
• Issued: 09/14/2004
• Est. Priority Date: 01/30/2002
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Schrödinger, Karl, Stimma, Jaro Robert
• Primary Examiner(s): Gutierrez, Diego
• Assistant Examiner(s): Jagan, Mirellys
• Application Number:
  US10/217,912
• Publication Number:
  US 20030141920A1
• Time in Patent Office: 763 Days
• Field of Search: 374/171, 374/173, 374/178, 327/512, 330/289
• US Class Current: 374/178
• CPC Class Codes: G01K 7/01 using semiconducting elements having PN junctions G01K7/02, G01K7/16, G01K7/30 take precedence

Abstract

The invention relates to a temperature sensor having a first FET transistor circuit and a second FET transistor circuit and also to a method for operating a temperature sensor. Both FET transistor circuits are operated at an operating point that lies outside the temperature-independent operating point. The difference between the voltages at the first and second FET transistor circuits is evaluated as a measure of the temperature at one of the FET transistor circuits. The invention enables the temperature sensor to provide a relatively large output signal even in the case of only small changes in temperature.

Claims

1. A temperature sensor, comprising:

a first FET transistor circuit and a second FET transistor circuit each having a gate voltage and a temperature-independent operating point at which, for a constant drain-source current, the gate voltage is essentially temperature-independent;

a circuit for operating said first FET transistor circuit at a first operating point being different from said temperature-independent operating point, said circuit also being for operating said second FET transistor circuit at a second operating point being different from said temperature-independent operating point;

said first FET transistor circuit providing a first voltage;

said second FET transistor circuit providing a second voltage; and

a difference between the first voltage and the second voltage being evaluated as a measure of a temperature at a transistor circuit selected from a group consisting of said first FET transistor circuit and said second FET transistor circuit.

2. The temperature sensor according to claim 1, wherein:

said first operating point is above said temperature-independent operating point; and

said second operating point is below said temperature-independent operating point.

3. The temperature sensor according to claim 1, wherein:

said first operating point is above said temperature-independent operating point; and

said second operating point is above said temperature-independent operating point.

4. The temperature sensor according to claim 1, wherein:

said first operating point is below said temperature-independent operating point; and

said second operating point is below said temperature-independent operating point.

5. The temperature sensor according to claim 1, wherein:

said circuit includes a resistor connected in series with said first FET transistor circuit; and

said circuit includes a resistor connected in series with said second FET transistor circuit.

6. The temperature sensor according to claim 1, wherein:

said first FET transistor circuit includes a FET transistor that is connected to form a diode; and

said second FET transistor circuit includes a FET transistor that is connected to form a diode.

7. The temperature sensor according to claim 1, wherein:

a transistor circuit selected from a group consisting of said first FET transistor circuit and said second FET transistor circuit includes a plurality of FET transistors connected in series.

8. The temperature sensor according to claim 1, wherein:

said first operating point is below said temperature-independent operating point; and

said second operating point is above said temperature-independent operating point.

9. The temperature sensor according to claim 1, comprising:

an amplifier circuit for detecting the difference between the first voltage and the second voltage and for converting the difference into a control voltage.

10. The temperature sensor according to claim 9, comprising:

a further amplifier circuit receiving the control voltage.

11. The temperature sensor according to claim 1, wherein:

said circuit includes a current generator that feeds constant currents to said first FET transistor circuit and to said second FET transistor circuit.

12. The temperature sensor according to claim 11, wherein:

said current generator includes a current mirror that defines the first operating point and the second operating point.

13. The temperature sensor according to claim 11, wherein:

said current generator includes two coupled current sources that feed said first FET transistor circuit and said second FET transistor circuit.

14. The temperature sensor according to claim 13, wherein:

said current generator includes a current mirror that defines the first operating point and the second operating point.

15. A temperature sensor, comprising:

a first FET transistor circuit and a second FET transistor circuit each having a gate voltage and a temperature-independent operating point at which, for a constant drain-source current, the gate voltage is essentially temperature-independent;

a circuit for operating said first FET transistor circuit at a first operating point being different from said temperature-independent operating point, said circuit also being for operating said second FET transistor circuit at a second operating point being different from said temperature-independent operating point;

said first FET transistor circuit providing a first voltage;

said second FET transistor circuit providing a second voltage;

a difference between the first voltage and the second voltage being evaluated as a measure of a temperature at a transistor circuit selected from a group consisting of said first FET transistor circuit and said second FET transistor circuit; and

an amplifier circuit detecting a difference in said gate voltages at said first and said second FET transistor circuits, and for converting the difference into a control voltage for controlling the current source of a further amplifier circuit.

16. The temperature sensor according to claim 15, wherein said control voltage forms a gate voltage of a FET transistor, said gate voltage of said FET transistor is a current source for a differential amplifier.

17. A method for operating a temperature sensor, which comprises:

providing the temperature sensor with a first FET transistor circuit, a second FET transistor circuit, and a circuit for operating the first FET transistor circuit and the second FET transistor circuit;

evaluating a difference between a voltage at the first FET transistor circuit and a voltage at the second FET transistor circuit as a measure of a temperature at a transistor circuit selected from a group consisting of the first FET transistor circuit and the second FET transistor circuit;

providing the first FET transistor circuit and the second FET transistor circuit with a temperature-independent operating point at which, for a constant drain-source current, a gate voltage is essentially temperature-independent; and

operating the first FET transistor circuit and the second FET transistor circuit at a respective operating point that is different from the temperature-independent operating point.

18. The method according to claim 17, which comprises:

operating the first FET transistor circuit above the temperature-independent operating point; and

operating the second FET transistor circuit below the temperature-independent operating point.

19. The method according to claim 17, which comprises:

operating the second FET transistor circuit above the temperature-independent operating point; and

operating the first FET transistor circuit below the temperature-independent operating point.

20. The method according to claim 17, which comprises:

operating the first FET transistor circuit above the temperature-independent operating point; and

operating the second FET transistor circuit above the temperature-independent operating point.

21. The method according to claim 17, which comprises:

operating the first FET transistor circuit below the temperature-independent operating point; and

operating the second FET transistor circuit below the temperature-independent operating point.

22. A method for operating a temperature sensor, which comprises:

providing the temperature sensor with a first FET transistor circuit, a second FET transistor circuit, and a circuit for operating the first FET transistor circuit and the second FET transistor circuit;

evaluating a difference between a voltage at the first FET transistor circuit and a voltage at the second FET transistor circuit as a measure of a temperature at a transistor circuit selected from a group consisting of the first FET transistor circuit and the second FET transistor circuit;

providing the first FET transistor circuit and the second FET transistor circuit with a temperature-independent operating point at which, for a constant drain-source current, a gate voltage is essentially temperature-independent; and

operating the first FET transistor circuit and the second FET transistor circuit at a respective operating point that is different from the temperature-independent operating point;

detecting the difference between the first voltage and the second voltage and converting the difference into a control voltage using an amplifier circuit; and

controlling a further amplifier circuit using the control voltage.