Semiconductor memory device

1. A semiconductor memory device, comprising:

a first memory cell having a first end electrically connected to a first wiring and a second end electrically connected to a second wiring;

a second memory cell having a first end electrically connected to the first wiring and a second end electrically connected to a third wiring; and

a sense amplifier configured to:

sense a first current flowing in the first wiring when a first voltage is applied to the second and third wirings and a second voltage, larger than the first voltage, is applied to the first wiring,

sense a second current flowing in the first wiring when a third voltage, larger than the second voltage, is applied to the first wiring, the first voltage is applied to the second wiring, and the second voltage is applied to the third wiring, and

read data from the first memory cell according to a difference between the first current and the second current.

2. The semiconductor memory device according to claim 1 , further comprising:

a third memory cell;

a first transistor having a first end electrically connected to the first wiring and a second end electrically connected to the first end of the first memory cell and the first end of the second memory cell; and

a second transistor having a first end electrically connected to the first wiring and a second end electrically connected to a first end of the third memory cell, wherein

the sense amplifier is configured to sense the first current and the second current when the first transistor is in an on state and the second transistor is in an off state.

3. The semiconductor memory device according to claim 1 , further comprising:

a fourth memory cell having a first end electrically connected to a fourth wiring and a second end electrically connected to one of the second wiring or the third wiring, wherein

the sense amplifier is configured to:

sense the first current when the first voltage is applied to the fourth wiring; and

sense the second current when the second voltage is applied to the fourth wiring.

4. The semiconductor memory device according to claim 1 , further comprising:

a fourth memory cell having a first end electrically connected to a fourth wiring and a second end electrically connected to one of the second wiring or the third wiring, wherein

the sense amplifier is configured to sense the first current and the second current when the first voltage is applied to the fourth wiring.

5. The semiconductor memory device according to claim 1 , wherein the sense amplifier includes:

a first current mirror circuit having a first end electrically connected to the first wiring;

a first capacitor and a second capacitor, each including a first end electrically connected to a second end of the first current mirror circuit;

a third transistor having a gate node electrically connected to the first end of the first capacitor;

a fourth transistor having a gate node electrically connected to the first end of the second capacitor;

a second current mirror circuit having a first end electrically connected to a first end of the fourth transistor and a second end electrically connected to a first end of the third transistor; and

a third capacitor having a first end electrically connected to the first end of the third transistor and the second end of the second current mirror circuit.

6. The semiconductor memory device according to claim 5 , wherein the sense amplifier further includes:

a fifth transistor having a first end electrically connected to the second end of the first current mirror circuit and a second end electrically connected to the first end of the first capacitor; and

a sixth transistor having a first end electrically connected to the second end of the first current mirror circuit and the first end of the fifth transistor and a second end electrically connected to the first end of the second capacitor.

7. The semiconductor memory device according to claim 6 , wherein the sense amplifier is configured to:

place the fifth transistor into an on state and the sixth transistor into an off state when sensing the first current; and

place the fifth transistor into an off state and the sixth transistor into an on state when sensing the second current.

8. The semiconductor memory device according to claim 5 , wherein the sense amplifier further includes:

a first comparator having a first input electrically connected to the first end of the third capacitor and a second input to which a fourth voltage is applied.

9. The semiconductor memory device according to claim 8 , wherein the sense amplifier further includes:

N second comparators, where N is an integer equal to or greater than 1, each second comparator having a first input electrically connected to the first end of the third capacitor and a second input to which a voltage different from the fourth voltage is applied, and

the voltages applied to each respective second input of the N second comparators have different magnitudes.

10. The semiconductor memory device according to claim 1 , wherein the sense amplifier includes:

a first current mirror circuit having a first end electrically connected to the first wiring;

a first capacitor and a second capacitor, each having a first end electrically connected to a second end of the first current mirror circuit; and

a third transistor having a gate node electrically connected to the first end of the first capacitor and a first end electrically connected to the second end of the first current mirror circuit and the first end of the second capacitor.

11. The semiconductor memory device according to claim 10 , wherein the sense amplifier further includes:

a fourth transistor having a first end electrically connected to the second end of the first current mirror circuit and a second end electrically connected to the first end of the first capacitor; and

a fifth transistor including a first end electrically connected to the second end of the first current mirror circuit and the first end of the fourth transistor and a second end electrically connected to the first end of the second capacitor and the first end of the third transistor.

12. The semiconductor memory device according to claim 11 , wherein the sense amplifier is configured to:

place the fourth transistor into an on state and the fifth transistor into an off state when sensing the first current; and

place the fourth transistor into an off state and the fifth transistor into an on state when sensing the second current.

13. The semiconductor memory device according to claim 11 , wherein the sense amplifier is configured to:

place the fourth transistor into an off state and the fifth transistor into an on state when sensing the first current; and

place the fourth transistor into an on state and the fifth transistor into an off state when sensing the second current.

14. The semiconductor memory device according to claim 10 , wherein the sense amplifier further includes:

a first comparator having a first input electrically connected with the first end of the second capacitor and a second input to which the fourth voltage is applied.

15. The semiconductor memory device according to claim 14 , wherein the sense amplifier further includes:

N second comparators, where N is an integer equal to or greater than 1, each second comparator having a first input electrically connected to the first end of the second capacitor and a second input to which a voltage different from the fourth voltage is applied, and

the voltages applied to each respective second input of the N second comparators have different magnitudes.

16. The semiconductor memory device according to claim 10 , wherein the third transistor comprises a plurality of transistors which are connected to each other in parallel.

17. The semiconductor memory device according to claim 16 , wherein the sense amplifier is configured to vary the number of transistors in the plurality of transistors comprising the third transistor brought into an on state when sensing the second current according to a memory cell reading data.

18. The semiconductor memory device according to claim 1 , wherein the second voltage has an intermediate value between the first voltage and the third voltage.

19. The semiconductor memory device according to claim 1 , wherein the sense amplifier is configured to sense the second current after sensing the first current.

20. The semiconductor memory device according to claim 1 , wherein the sense amplifier is configured to sense the first current after sensing the second current.