Voltage comparator

A voltage comparator:

• a first and a second voltage supply terminal,
• a first and a second output node,
• a first and a second current source,
• said first current source connected between said first voltage supply terminal and said first output node,
• said second current source connected between said first voltage supply terminal and said second output node,
• a first capacitor and a second capacitor of substantially identical capacitance,
• said first capacitor connected between said first output node and said second voltage supply terminal,
• said second capacitor connected between said second output node and said second voltage supply terminal,
• a first and a second insulated-gate field-effect transistor of one channel conductivity type and of substantially identical structure,
• the channel of said first insulated-gate field-effect transistor connected between said first output node and said second voltage supply terminal,
• the channel of said second insulated-gate field-effect transistor connected between said second output node and said second voltage supply terminal,
• the gate of said first insulated-gate field-effect transistor connected to said second output node,
• the gate of said second insulated-gate field-effect transistor connected to said first output node,
• means for applying a first unidirectional voltage between said first and second voltage supply terminals,
• a first switching means for connecting said first output node to said second voltage supply terminal during a first period of time whereby the potential of said first output node is set to substantially the potential of said second voltage supply terminal during said first period of time,
• a second switching means for connecting said second output node to said second voltage supply terminal during said first period of time whereby the potential of said second output node is set to substantially the potential of said second voltage supply terminal during said first period of time,
• a third capacitor and a fourth capacitor of substantially identical capacitance, the capacitance of said third capacitor being comparable to the capacitance of said first capacitor,
• means for providing a first signal voltage,
• means for providing a second signal voltage less than said first signal voltage,
• a third switching means for charging said third capacitor to said first signal voltage during said first period of time,
• a fourth switching means for charging said fourth capacitor to said second signal voltage during said first period of time,
• a fifth switching means for connecting said third capacitor in parallel with said first capacitor at the end of said first period of time,
• a sixth switching means for connecting said fourth capacitor in parallel with said second capacitor at the end of said first period of time,
• whereby at the end of said first period of time the first and second capacitors and hence the gates of said first and second transistors are charged through said first current source and said second current source causing said second transistor to become conductive as the gate thereof has a greater initial voltage appearing thereon than the gate of said first transistor and causing said first transistor to remain nonconductive as the voltage on said second output node is fed back to the gate of said first transistor.