Thermal sensor circuit

1. A temperature sensing circuit, comprising:

a thermistor comprising a first MOS transistor having a first drain, a first source, a first gate and a first body, wherein the first MOS transistor is configured to operate in weak inversion mode with a negative temperature coefficient drain-source resistance;

an output terminal coupled to the first source and configured to generate a positive temperature coefficient output voltage; and

a current source comprising a second MOS transistor having a second drain, a second source, a second gate and a second body, wherein the second gate is coupled to the first source and configured to impose a drain-source of the first MOS transistor; and

an electrical connection directly between of each of the first body and second body and a ground node.

2. The temperature sensing circuit of claim 1 , wherein the first and second MOS transistors are supported by a bulk substrate that provides the first and second bodies.

3. The temperature sensing circuit of claim 1 , wherein the first and second MOS transistors are supported by a semiconductor on insulator (SOI) substrate, said SOI substrate including a semiconductor film layer over a buried oxide layer over a semiconductor substrate, and wherein the semiconductor film layer provides the first and second bodies.

4. The temperature sensing circuit of claim 3 , wherein the SOI substrate is one of a fully depleted SOI substrate or a partially depleted SOI substrate.

5. The temperature sensing circuit of claim 3 , wherein the first MOS transistor further has a first back gate and the second MOS transistor further has a second back gate, and wherein the first and second back gates are provided within the semiconductor substrate of the SOI substrate.

6. The temperature sensing circuit of claim 5 , comprising an electrical connection directly between each of the first and second back gates and the ground node.

7. The temperature sensing circuit of claim 1 , comprising an electrical connection directly between the first drain and a supply voltage node.

8. The temperature sensing circuit of claim 1 , comprising an electrical connection directly between each of the second source and second drain and the ground node.

9. The temperature sensing circuit of claim 1 , comprising an electrical connection directly between the second source and the ground node and wherein the second drain is not directly connected to the output terminal and further is configured to receive a bias voltage.

10. The temperature sensing circuit of claim 1 , comprising an electrical connection directly between the first gate and the first drain.

11. The temperature sensing circuit of claim 1 , wherein the first gate of the first MOS transistor has a first gate oxide thickness, and wherein the second gate of the second MOS transistor has a second gate oxide thickness, and wherein the first gate oxide thickness is thicker than the second gate oxide thickness.

12. The temperature sensing circuit of claim 11 , wherein the first and second MOS transistors are supported by a bulk substrate providing the first and second bodies.

13. The temperature sensing circuit of claim 11 , wherein the first and second MOS transistors are supported by a semiconductor on insulator (SOI) substrate, said SOI substrate including a semiconductor film layer over a buried oxide layer over a semiconductor substrate, and wherein the semiconductor film layer provides the first and second bodies.

14. The temperature sensing circuit of claim 13 , wherein the SOI substrate is a fully depleted SOI substrate or a partially depleted SOI substrate.

15. The temperature sensing circuit of claim 13 , wherein the first MOS transistor further has a first back gate and the second MOS transistor further has a second back gate, and wherein the first and second back gates are provided within the semiconductor substrate of the SOI substrate.

16. The temperature sensing circuit of claim 15 , comprising an electrical connection directly between each of the first and second back gates and the ground node.

17. The temperature sensing circuit of claim 11 , comprising an electrical connection directly between the first drain and a supply voltage node.

18. The temperature sensing circuit of claim 11 , comprising an electrical connection directly between each of the second source and second drain and the ground node.

19. The temperature sensing circuit of claim 11 , comprising an electrical connection directly between the second source and the ground node and wherein the second drain is not directly connected to the output terminal and further is configured to receive a bias voltage.

20. The temperature sensing circuit of claim 11 , comprising an electrical connection directly between the first gate and the first drain.

21. The temperature sensing circuit of claim 1 , wherein the thermistor further comprises:

a third MOS transistor coupled in series with the first MOS transistor and having a third drain which is coupled to the first source, a third source coupled to the output terminal, a third gate and a third body, wherein the third MOS transistor is configured to operate in weak inversion mode with a negative temperature coefficient drain-source resistance; and

an electrical connection directly between the third body and the ground node.

22. The temperature sensing circuit of claim 21 , wherein the first, second and third MOS transistors are supported by a bulk substrate providing the first, second and third bodies.

23. The temperature sensing circuit of claim 21 , wherein the first, second and third MOS transistors are supported by a semiconductor on insulator (SOI) substrate, said SOI substrate including a semiconductor film layer over a buried oxide layer over a semiconductor substrate, and wherein the semiconductor film layer provides the first, second and third bodies.

24. The temperature sensing circuit of claim 23 , wherein the SOI substrate is a fully depleted SOI substrate or a partially depleted SOI substrate.

25. The temperature sensing circuit of claim 23 , wherein the first MOS transistor further has a first back gate, the second MOS transistor further has a second back gate and the third MOS transistor further has a third back gate, and wherein the first, second and third back gates are provided within the semiconductor substrate of the SOI substrate.

26. The temperature sensing circuit of claim 25 , comprising an electrical connection directly between each of the first, second and third back gates and the ground node.

27. The temperature sensing circuit of claim 21 , comprising an electrical connection directly between the first drain and a supply voltage node.

28. The temperature sensing circuit of claim 21 , comprising an electrical connection directly between each of the second source and second drain and the ground node.

29. The temperature sensing circuit of claim 21 , comprising an electrical connection directly between the second source and the ground node and wherein the second drain is configured to receive a bias voltage.

30. The temperature sensing circuit of claim 21 , comprising an electrical connection directly between the first gate and the first drain and an electrical connection directly between the third gate and the third drain.

31. The temperature sensing circuit of claim 21 , wherein the first gate of the first MOS transistor has a first gate oxide thickness, wherein the second gate of the second MOS transistor has a second gate oxide thickness, wherein the third gate of the third MOS transistor has a third gate oxide thickness, and wherein the first and third gate oxide thicknesses are thicker than the second gate oxide thickness.

32. A temperature sensing circuit, comprising:

a first MOS transistor having a first drain, a first source, a first gate and a first body;

wherein the first gate is electrically shorted to the first drain;

wherein the first drain is coupled to a supply voltage node;

wherein the first MOS transistor has a negative temperature coefficient drain-source resistance; and

a second MOS transistor having a second drain, a second source, a second gate and a second body;

wherein the second gate is electrically shorted to the first source at an output terminal configured to generate a positive temperature coefficient output voltage;

wherein the first body and second body are each electrically shorted to a ground node; and

wherein the second source and second drain are each electrically shorted to the ground node.

33. A temperature sensing circuit, comprising:

a thermistor comprising a first MOS transistor having a first drain, a first source, a first gate and a first body, wherein the first MOS transistor is configured to operate in weak inversion mode with a negative temperature coefficient drain-source resistance;

an output terminal coupled to the first source and configured to generate a positive temperature coefficient output voltage; and

a current source comprising a second MOS transistor having a second drain, a second source, a second gate and a second body, wherein the second gate is coupled to the first source and configured to impose a drain-source of the first MOS transistor; and

wherein the first body and second body are directly physically connected to ground.

34. The temperature sensing circuit of claim 33 , wherein the second source and second drain are directly physically connected to ground.