Single-ended sense amplifier with adjustable noise margin and power down control

Claim 1

A single-ended sense amplifier for sensing a state of a first node, comprising: an output circuit having an input terminal and an output terminal, the output terminal indicating a state of the first node in response to a voltage level of the first node; a precharge circuit coupled to the input terminal for charging the input terminal in response to a first voltage level of a precharge signal; a noise margin circuit coupled to the first node for outputting a reference voltage by inverting the voltage level of the first node according to a first logic-threshold voltage in response to the first voltage level of the precharge signal and a second logic-threshold voltage in response to a second voltage level of the precharge signal; and a first n-channel transistor having a drain coupled to the input terminal of said output circuit, a source coupled to the first node, and a gate for receiving the reference voltage, and characterized in that said noise margin circuit comprises: a first p-channel transistor having a source coupled to an external voltage source, a drain coupled to the gate of said first n-channel transistor, and a gate coupled to the first node; a second n-channel transistor having a drain coupled to the gate of said first n-channel transistor, a grounded source, and a gate coupled to the first node; a second p-channel transistor having a source, a drain coupled to the gate of said first n-channel transistor, and a gate coupled to the first node; and a third p-channel transistor having a source coupled to the external voltage source, a drain coupled to the source of said second p-channel transistor, and a gate for receiving the precharge signal; wherein an inverter with the second logic-threshold voltage substantially consisting of said first p-channel transistor and said second n-channel transistor is effectively operated in response to the second voltage level of the precharge signal being higher than the first voltage level of the precharge signal by turning said second p-channel transistor and said third p-channel transistor off, and an inverter with the first logic-threshold voltage substantially consisting of said first p-channel transistor, said second n-channel transistor, said second p-channel transistor, and said third p-channel transistor is effectively operated in response to the first voltage level of the precharge signal by turning said second p-channel transistor and said third p-channel transistor on, in such a way that first logic-threshold voltage of said noise margin circuit is higher than the second logic-threshold voltage of the noise margin circuit.