Current sense amplifiers, memory devices and methods
A current sense amplifier may include one or more clamping circuits coupled between differential output nodes of the amplifier. The clamping circuits may be enabled during at least a portion of the time that the sense amplifier is sensing the state of a memory cell coupled to a differential input of the sense amplifier. The clamping circuits may be disabled during the time that the sense amplifier is sensing the state of a memory cell at different times in a staggered manner. The clamping circuits may be effecting in making the current sense amplifier less sensitive to noise signals.
1. An amplifier, comprising:
a first transistor of a first conductivity type coupled between first and second nodes;
a second transistor of the first conductivity type coupled between third and fourth nodes, a control gate of the first transistor being coupled to the third node and a control gate of the second transistor being coupled to the first node;
a first clamp circuit coupled between the first and third nodes and configured to form a current path between the first and third nodes responsive to a first clamp signal;
a second clamp circuit coupled between the first and third nodes and configured to form a current path between the first and third nodes responsive to a second clamp signal;
first and second resistors coupled between the first clamp circuit and the second clamp circuit; and
a control circuit configured to provide the first clamp signal to the first clamp circuit and to stop provision of the first clamp signal to the first clamp circuit after the amplifier has been enabled, and to provide the second clamp signal to the second clamp circuit and to stop provision of the second clamp signal to the second clamp circuit after the amplifier has been enabled.
2. The amplifier as claimed in claim 1 , wherein the control circuit is configured to stop provision of the first clamp signal to the first clamp circuit during a time when the amplifier is enabled.
3. The amplifier as claimed in claim 2 , wherein, after provision of the first clamp signal has been stopped, the control circuit is configured to provide the first clamp signal to the first clamp circuit before the amplifier is disabled.
4. The amplifier as claimed in claim 1 , wherein the control circuit is configured to stop provision of the second clamp signal to the second clamp circuit during a time when the amplifier is enabled and after terminating provision of the first clamp signal to the first clamp circuit.
5. The amplifier as claimed in claim 4 , wherein, after provision of the second clamp signal has been stopped, the control circuit is configured to provide the second clamp signal to the second clamp circuit before the amplifier is disabled.
6. The amplifier as claimed in claim 1 , the amplifier further comprising:
a first resistor coupled between the clamp circuit and the first node; and
a second resistor coupled between the clamp circuit and the third node.
7. The amplifier as claimed in claim 1 , wherein the first node is a first output node, the second node is a first input node, the third node is a second output node and the fourth node is a second input node.
8. An amplifier, comprising:
a first transistor of a first conductivity type coupled between first and second nodes;
a second transistor of the first conductivity type coupled between third and fourth nodes, a control gate of the first transistor being coupled to the third node and a control gate of the second transistor being coupled to the first node;
a third transistor of the first conductivity type coupled between the second node and a fifth node;
a fourth transistor of the first conductivity type coupled between the fourth node and a sixth node, the fifth and sixth nodes being supplied with a first power source potential, the third and fourth transistors being configured to form a current path between the second and fifth nodes and between the fourth and sixth nodes, respectively, responsive to a receipt of an enable information at control gates of the third and fourth transistors;
a fifth transistor of a second conductivity type coupled between the first node and a seventh node;
a sixth transistor of the second conductivity type coupled between the third node and an eighth node, the seventh and eighth nodes being supplied with a second power source potential, the fifth and sixth transistors being configured to form a current path between the first and seventh nodes and between the third and eighth nodes, respectively, responsive to a receipt of the enable information at control gates of the fifth and sixth transistors;
a clamp circuit coupled between the first and third nodes and configured to form a current path between the first and third nodes responsive to a clamp signal; and
a control circuit configured to provide an active clamp signal to actuate the clamp circuit before control gates of the third, fourth, fifth and sixth transistors receive active enable information and maintain provision of the active clamp signal to the clamp circuit after the control gates of the third, fourth, fifth and sixth transistors receive the active enable information.
9. The amplifier as claimed in claim 8 , wherein the control circuit is configured to terminate provision of the active clamp signal to deactivate the clamp circuit during a time when the control gates of the third, fourth, fifth and sixth transistors receive active the enable information.
10. The amplifier as claimed in claim 9 , wherein, after terminating provision of the active clamp signal to the clamp circuit, the control circuit is configured to provide the clamp signal to actuate the clamp circuit before the control gates of the third, fourth, fifth and sixth transistors stop reception of the active enable information.
11. The amplifier as claimed in claim 8 ,
wherein the clamp circuit is a first clamp circuit and the clamp signal is a first clamp signal, the amplifier further comprising:
a second clamp circuit coupled between the first and third nodes and configured to form a current path between the first and third nodes responsive to a second clamp signal,
wherein the control circuit configured to provide an active second clamp signal to actuate the second clamp circuit before control gates of the third, fourth, fifth and sixth transistors receive the active enable information, maintain provision of the active second clamp signal to the second clamp circuit after the control gates of the third, fourth, fifth and sixth transistors receive the active enable information, and terminate provision of the active second clamp signal to deactivate the second clamp circuit after terminating provision of the active first clamp signal to deactivate the first clamp circuit.
12. The amplifier as claimed in claim 11 , wherein, after provision of the active second clamp signal has been terminated, the control circuit is configured to provide the second clamp signal to actuate the second clamp circuit before the control gates of the third, fourth, fifth and sixth transistors are terminated receiving the active enable information.
13. The amplifier as claimed in claim 11 , the amplifier further comprising:
a first resistor coupled between a connecting point of the first transistor and the first clamp circuit and a connecting point of the fifth transistor and the second clamp circuit; and
a second resistor coupled between a connecting point of the second transistor and the first clamp circuit and a connecting point of the sixth transistor and the second clamp circuit.
14. The amplifier as claimed in claim 8 , the amplifier further comprising:
a first resistor coupled between the first node and a connecting point of the fifth transistor and the clamp circuit; and
a second resistor coupled between the second node and a connecting point of the sixth transistor and the clamp circuit.
15. The amplifier as claimed in claim 8 , wherein the first node is a first output node, the second node is a first input node, the third node is a second output node and the fourth node is a second input node.
16. An amplifier, comprising:
a first transistor of a first conductivity type coupled between first and second nodes;
a second transistor of the first conductivity type coupled between third and fourth nodes, a control gate of the first transistor being coupled to the third node and a control gate of the second transistor being coupled to the first node;
a first clamp circuit coupled between the first and third nodes and configured to form a current path between the first and third nodes responsive to a first clamp signal;
a second clamp circuit coupled between the first and third nodes and configured to form a current path between the first and third nodes responsive to a second clamp signal; and
first and second resistors coupled between the first clamp circuit and the second clamp circuit.
17. The amplifier as claimed in claim 16 , the amplifier further comprising:
a control circuit configured to provide the first clamp signal and the second clamp signal, wherein timing of provision of the first clamp signal is different than timing of provision of the second clamp signal.
18. The amplifier as claimed in claim 17 , wherein timing of transition from active to inactive for the first clamp signal is different than timing of transition from active to inactive for the second clamp signal, wherein timing of transition from inactive to active for the first clamp signal is equal to timing of transition from inactive to active for the second clamp signal.