Integrated circuit having a switch

1. An integrated circuit having a switch comprising:

a first resistivity changing element;

a first reference element;

a second reference element; and

a sense amplifier, the sense amplifier configured to compare a signal from the first resistivity changing element to a signal from the first reference element and to output a first signal based on the comparison for configuring the integrated circuit, the sense amplifier further configured to compare the signal from the first resistivity changing element to a signal from the second reference element and to output a second signal based on the comparison for configuring the integrated circuit.

2. The integrated circuit of claim 1 , wherein the first reference element comprises a second resistivity changing element.

3. The integrated circuit of claim 2 , wherein the second reference element comprises a third resistivity changing element.

4. The integrated circuit of claim 1 , wherein the first reference element comprises a first resistor.

5. The integrated circuit of claim 4 , wherein the second reference element comprises a second resistor.

6. The integrated circuit of claim 1 , wherein the first resistivity changing element can be programmed to each one of at least three resistance values.

7. The integrated circuit of claim 1 , further comprising:

a third reference element,

wherein the sense amplifier is further configured to compare the signal from the first resistivity changing element to a signal from the third reference element and to output a third signal based on the comparison for configuring the integrated circuit.

8. A reprogrammable switch comprising:

phase-change material; and

a sense amplifier coupled to the phase-change material, a first reference signal, and a second reference signal, the sense amplifier configured to compare a signal from the phase-change material to the first reference signal to provide a first output signal for deactivating a failing portion of a chip, the sense amplifier further configured to compare the signal from the phase-change material to the second reference signal to provide a second output signal for deactivating a failing portion of the chip.

9. The switch of claim 8 , wherein the first reference signal comprises a first voltage, the second reference signal comprises a second voltage, and the signal from the phase-change material comprises a third voltage.

10. The switch of claim 8 , wherein the first reference signal comprises a first current, the second reference signal comprises a second current, and the signal from the phase-change material comprises a third current.

11. A reprogrammable switch comprising:

a first phase-change element;

a first reference element directly coupled to the first phase-change element;

a second reference element directly coupled to the first reference element;

a first transistor directly coupled to the first phase-change element and the first reference element, the first transistor turning on based on a state of the first phase-change element; and

a second transistor directly coupled to the first reference element and the second reference element, the second transistor turning on based on a state of the first phase-change element.

12. The switch of claim 11 , wherein the first reference element comprises a second phase-change element, and

wherein the first transistor turns on based on a state of the first phase-change element and a state of the second phase-change element.

13. The switch of claim 12 , wherein the second reference element comprises a third phase-change element, and

wherein the second transistor turns on based on a state of the first phase-change element and a state of the third phase-change element.

14. The switch of claim 11 , wherein the first reference element comprises a first resistor.

15. The switch of claim 14 , wherein the second reference element comprises a second resistor.

16. The switch of claim 11 , wherein the first phase-change element can be programmed to each one of at least three resistance values.

17. The switch of claim 11 , further comprising:

a third reference element coupled to the second reference element; and

a third transistor coupled to the second reference element and the third reference element, the third transistor turning on based on a state of the first phase-change element.

18. A reprogrammable switch comprising:

phase-change material;

a first reference element;

a second reference element; and

means for deactivating a first failing portion of an integrated circuit based on a state of the first reference element and a state of the phase-change material and for deactivating a second failing portion of the integrated circuit based on a state of the second reference element and the state of the phase-change material.

19. The switch of claim 18 , wherein the phase-change material can be programmed to each one of at least three resistance values.

20. The switch of claim 18 , wherein the phase-change material comprises one of Ge, Sb, Te, Ga, As, In, Se, and S.

21. A method for using a reprogrammable switch, the method comprising:

applying a write pulse to a first phase-change material to switch a state of the first phase-change material;

applying a first signal to the first phase-change material, a first reference element, and a second reference element;

sensing a second signal from the first phase-change material, a third signal from the first reference element, and a fourth signal from the second reference element;

comparing the second signal to the third signal to provide a fifth signal;

configuring an integrated circuit based on the fifth signal;

comparing the second signal to the fourth signal to provide a sixth signal; and

configuring the integrated circuit based on the sixth signal.

22. The method of claim 21 , wherein applying the first signal to the first reference element comprises applying the first signal to second phase-change material.

23. The method of claim 21 , wherein applying the first signal to the first reference element comprises applying the first signal to a resistor.

24. A method for using a reprogrammable switch, the method comprising:

applying a write pulse to first phase-change material to program the first phase-change material;

dividing a first voltage between the first phase-change material, a first reference element, and a second reference element to provide a second voltage and a third voltage;

turning on a first switch based on the second voltage;

configuring an integrated circuit with the first switch;

turning on a second switch based on the third voltage; and

configuring the integrated circuit with the second switch.

25. The method of claim 24 , wherein dividing the first voltage comprises dividing the first voltage between the first phase-change material, the first reference element comprising a first static resistor, and the third reference element comprising a second static resistor.

26. The method of claim 24 , wherein dividing the first voltage comprises dividing the first voltage between the first phase-change material, the first reference element comprising a second phase-change material, and the third reference element comprising a third phase-change material.

27. The method of claim 24 , wherein turning on the first switch comprises turning on a first transistor switch, and

wherein turning on the second switch comprises turning on a second transistor switch.

28. An integrated circuit comprising:

a resistivity changing element;

a reference element; and

a sense amplifier continuously electrically coupled to the resistivity changing element and continuously providing an output signal based on a state of the resistivity changing element and a state of the reference element for deactivating a failing portion of the integrated circuit.