Patent ID: 6707410
Filing Date: 2004-03-16
Classification: G11C,H03K,H03M,H04N

Abstract:
A method for comparing a first signal and a second signal, comprising:precharging a source of a first input transistor to a first voltage, said first voltage being at a fixed offset less than a threshold voltage of said first input transistor; precharging a source of a second input transistor to a second voltage, said second voltage being at the fixed offset less than a threshold voltage of said second input transistor; coupling said first signal to a gate of said first input transistor; coupling said second signal to a gate of said second input transistor; sinking a first current through said first input transistor at a first rate related to a difference between a voltage of said first signal and said first voltage; sinking a second current through said second input transistor at a second rate related to a difference between a voltage of said second signal and said second voltage; if said first input transistor sinks a predetermined amount of current before said second input transistor, latching a first output node to a first predetermined voltage and latching a second output node to a second predetermined voltage; and if said second input transistor sinks a predetermined amount of current before said first input transistor, latching the second output node to the first predetermined voltage and latching the first output node to the second predetermined voltage; wherein said step of precharging a source of a first input transistor comprises, coupling a capacitor to said source of said first input transistor; discharging said capacitor by coupling both plates of said capacitor to ground; coupling a power supply voltage to a drain of said first input transistor; and coupling a bias voltage to a gate of said first input transistor, wherein said first input transistor conducts between the source and the drain until a voltage at the source is equal to the power supply voltage minus the threshold voltage of said first transistor.