Apparatus for increasing the input noise margin of a gate

Apparatus for a gate having an increased noise margin, said apparatus comprising:

• switching means, connected to a first fixed voltage source and to a circuit node and having a digital input responsive to a digital input signal, for causing current to flow from said first fixed voltage source to said circuit node whenever said digital input signal assumes an appropriate logical value;
• a current sink, connected to said circuit node and to a second fixed voltage source and operative in response to a feedback signal, for causing current to flow from said circuit node to said second fixed voltage source in response to said feedback signal;
• and
• means, connected to said circuit node and being responsive to a voltage appearing at said circuit node, for generating said feedback signal, wherein whenever the value of the voltage appearing at said circuit node reaches an appropriate level said feedback signal momentarily activates said current sink to impart a momentary step change to the voltage appearing at said circuit node such that a portion of said step change is applied through said switching means to said digital input in order to momentarily increase the noise margin of the gate.

Apparatus for a gate having an increased noise margin, said apparatus comprising:

• switching means, connected to a first fixed voltage source and to a circuit node and having a digital input responsive to a digital input signal, for causing current to flow from said first fixed voltage source to said circuit node whenever said digital input signal assumes an appropriate logical value;
• a current sink, connected to said circuit node and to a second fixed voltage source and operative in response to a feedback signal, for causing current to flow from said current node to said second fixed voltage source in response to said feedback signal;
• said current sink having a first transistor with an emitter, a base and a collector, wherein the collector of the first transistor is connected through a first resistor to said circuit node, the emitter of the first transistor is connected through a diode to said second fixed voltage source and the base of the first transistor is connected to said feedback signal;
• and
• means, connected to said circuit node and being responsive to a voltage appearing at said circuit node, for generating said feedback signal, wherein whenever the value of the voltage appearing at said circuit node reaches an appropriate level said feedback signal momentarily activates said current sink to impart a momentary step change to the voltage appearing at said circuit node such that a portion of said step change is applied through said switching means to said digital input in order to momentarily increase the noise margin of the gate;
• said generating means having a second transistor with an emitter, a base and a collector, wherein the collector of said second transistor is connected through a second resistor to a third fixed voltage source, said base of said second transistor is connected to said circuit node and said emitter is connected through a third resistor to said second fixed voltage source, and wherein the collector of said second transistor is connected to the base of said first transistor such that the voltage appearing at the collector of said second transistor is said feedback signal.