Sense amplifier circuits and methods of operation

Patent metadata

Field	Value
Publication number	US-9697891-B2
Application number	US-201615341151-A
Country	US
Kind code	B2
Filing date	Nov 2, 2016
Priority date	Feb 26, 2009
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

A sense amplifier circuit includes a power node having a power node voltage at a power voltage level, a bit line having a bit line voltage, a sense amplifier output, an NMOS transistor and a PMOS transistor coupled in series between the power node and the bit line, and a logic gate configured to generate a sense amplifier output voltage at the sense amplifier output based on the bit line voltage. The NMOS transistor is configured to operate in a sub-threshold region to maintain the bit line voltage at a first level and operate in a region above the sub-threshold region to maintain the bit line voltage at a second level, and the first level is between the second level and the power voltage level.

First claim

What is claimed is:

1. A sense amplifier circuit comprising:
a power node having a power node voltage at a power voltage level;
a bit line having a bit line voltage;
a sense amplifier output;
an NMOS transistor and a PMOS transistor coupled in series between the power node and the bit line; and
a logic gate configured to generate a sense amplifier output voltage at the sense amplifier output based on the bit line voltage,
wherein
the NMOS transistor is configured to operate in a sub-threshold region to maintain the bit line voltage at a first level and operate in a region above the sub-threshold region to maintain the bit line voltage at a second level, and
the first level is between the second level and the power voltage level.

2. The sense amplifier circuit of claim 1 , wherein the second level and the power voltage level differ by at least a threshold voltage value of the NMOS transistor.

3. The sense amplifier circuit of claim 1 , wherein the NMOS transistor is configured to operate in the sub-threshold region and in the region above the sub-threshold region by a gate of the NMOS transistor having the power voltage level.

4. The sense amplifier of claim 3 , wherein the gate of the NMOS transistor is directly coupled to the power node.

5. The sense amplifier of claim 3 , wherein the gate of the NMOS transistor is selectively coupled to the power node by the PMOS transistor.

6. The sense amplifier circuit of claim 1 , wherein the PMOS transistor is configured to selectively couple the NMOS transistor to the power node or the bit line responsive to the sense amplifier output voltage.

7. The sense amplifier circuit of claim 1 , wherein the bit line is coupled to one or more pass gates of a static random access memory (SRAM) or register circuit, and the NMOS transistor is configured to compensate a leakage current through the one or more pass gates.

8. The sense amplifier of claim 1 , wherein the logic gate is an inverter.

9. The sense amplifier of claim 1 , wherein the logic gate is a noise resistant NAND gate.

10. The sense amplifier of claim 9 , wherein the noise resistant NAND gate comprises a half-Schmitt trigger circuit or a Schmitt trigger circuit.

11. The sense amplifier circuit of claim 1 , wherein the logic gate is a NAND gate, and the sense amplifier circuit further comprises a threshold control circuit configured to lower a trip point of the sense amplifier output.

12. A sense amplifier circuit comprising:
a power node having a power node voltage at a power voltage level;
a first bit line having a first bit line voltage;
a second bit line having a second bit line voltage;
a first NMOS transistor and a first PMOS transistor coupled in series between the power node and the first bit line; and
a NAND gate configured to generate a sense amplifier output voltage based on the first bit line voltage and the second bit line voltage,
wherein
the first NMOS transistor is configured to operate in a sub-threshold region to maintain the first bit line voltage at a first level and operate in a region above the sub-threshold region to maintain the first bit line voltage at a second level, and
the first level is between the second level and the power voltage level.

13. The sense amplifier circuit of claim 12 , wherein the second level and the power voltage level differ by at least a threshold voltage value of the first NMOS transistor.

14. The sense amplifier circuit of claim 12 , wherein the first NMOS transistor is configured to operate in the sub-threshold region and in the region above the sub-threshold region by a gate of the first NMOS transistor having the power voltage level.

15. The sense amplifier circuit of claim 12 , further comprising a second NMOS transistor and a second PMOS transistor coupled in series between the power node and the second bit line,
wherein
the second NMOS transistor is configured to operate in a second sub-threshold region to maintain the second bit line voltage at a third level and operate in a second region above the second sub-threshold region to maintain the second bit line voltage at a fourth level, and
the third level is between the fourth level and the power voltage level.

16. The sense amplifier circuit of claim 12 , further comprising a second PMOS transistor coupled between the first NMOS transistor and the second bit line,
wherein the first NMOS transistor is configured to operate in the sub-threshold region to maintain the second bit line voltage at the first level and operate in the region above the sub-threshold region to maintain the second bit line voltage at the second level.

17. A method of maintaining a bit line voltage of a bit line of a sense amplifier circuit, the method comprising:
providing a power supply voltage at a power supply node, the power supply voltage having a power supply voltage level;
selectively coupling the bit line to the power supply node using an NMOS transistor in series with a PMOS transistor;
operating the NMOS transistor in a sub-threshold region to maintain the bit line voltage at a first level;
operating the NMOS transistor above the sub-threshold region to maintain the bit line voltage at a second level, the first level being between the second level and the power supply voltage level;
receiving the bit line voltage with a logic gate; and
driving a sense amplifier output with the logic gate.

18. The method of claim 17 , wherein each of operating the NMOS transistor in the sub-threshold region and operating the NMOS transistor above the sub-threshold region comprises driving a gate of the NMOS transistor to the power supply voltage level.

19. The method of claim 18 , wherein driving the gate of the NMOS transistor to the power supply voltage level comprises coupling the gate of the NMOS transistor to the power supply node using the PMOS transistor responsive to the sense amplifier output.

20. The method of claim 17 , wherein at least one of operating the NMOS transistor in the sub-threshold region to maintain the bit line voltage at the first level or operating the NMOS transistor above the sub-threshold region to maintain the bit line voltage at the second level comprises offsetting a leakage current through one or more pass gates of a static random access memory (SRAM) or register circuit.

Assignees

• Taiwan Semiconductor Mfg Co Ltd

Inventors

• Upputuri Bharath

Classifications

• G11C11/419 Primary

  Read-write [R-W] circuits · CPC title

• G11C11/418

  Address circuits · CPC title

• G11C7/067 Primary

  Single-ended amplifiers · CPC title

• G11C11/413

  Auxiliary circuits, e.g. for addressing, decoding, driving, writing, sensing, timing or power reduction · CPC title