Patent ID: 6337582
Filing Date: 2002-01-08
Classification: G11C

Abstract:
A buffer circuit comprising:(a) a first inverter circuit including a first MOSFET having a channel of a first conductivity type and a second MOSFET having a channel of a second conductivity type opposite to the first conductivity type; a gate of said first MOSFET and a gate of said second MOSFET being coupled together, forming an input terminal of said first inverter circuit; a first input signal at a first logic state being applied to the input terminal of said first inverter circuit; one end of the channel of said first MOSFET and one end of the channel of said second MOSFET being coupled together, forming an output terminal of said first inverter circuit; (b) a second inverter circuit including a third MOSFET having a channel of the first conductivity type and a fourth MOSFET having a channel of the second conductivity type; a gate of said third MOSFET and a gate of said fourth MOSFET being coupled together, forming an input terminal of said second inverter circuit; a second input signal at a second logic state opposite to the first logic state being applied to the input terminal of said second inverter circuit; one end of the channel of said third MOSFET and one end of the channel of said fourth MOSFET being coupled together, forming an output terminal of said second inverter circuit; (c) an equalization circuit for equalizing the first output signal of said first inverter circuit and the second output signal of said second inverter circuit to each other; said equalization circuit including a fifth MOSFET having a channel of the first conductivity type and a sixth MOSFET having a channel of the second conductivity type; one end of the channel of said fifth MOSFET and one end of the channel of said sixth MOSFET being coupled together to be connected to the output terminal of said first inverter circuit; the other end of the channel of said fifth MOSFET and the other end of the channel of said sixth MOSFET being coupled together to be connected to the output terminal of said second inverter circuit; gates of said fifth and sixth MOSFETs being respectively applied with control signals at opposite logic levels, thereby setting said equalization circuit in a high-impedance state or a low-impedance state; (d) a first switching circuit for connecting the other end of the channel of said first MOSFET to a first voltage line or disconnecting it from the first voltage line; said first switching circuit including a seventh MOSFET having a channel of the first conductivity type; one end of the channel of said seventh MOSFET being connected to the other end of the channel of said first MOSFET; said first switching circuit being switched by a control signal applied to a gate of said seventh MOSFET; (e) a second switching circuit for connecting the other end of the channel of said second MOSFET to a second voltage line or disconnecting it from the second voltage line; said second switching circuit including an eighth MOSFET having a channel of the second conductivity type; one end of the channel of said eighth MOSFET being connected to the other end of the channel of said second MOSFET; said second switching circuit being switched by a control signal applied to a gate of said eighth MOSFET; (f) a third switching circuit for connecting the other end of the channel of said third MOSFET to the first voltage line or disconnecting it from the first voltage line; said third switching circuit including a ninth MOSFET having a channel of the first conductivity type; one end of the channel of said ninth MOSFET being connected to the other end of the channel of said third MOSFET; said third switching circuit being switched by a control signal applied to a gate of said ninth MOSFET; (g) a fourth switching circuit for connecting the other end of the channel of said fourth MOSFET to the second voltage line or disconnecting it from the second voltage line; said fourth switching circuit including a tenth MOSFET having a channel of the second conductivity type; one end of the channel of said tenth MOSFET being connected to the other end of the channel of said fourth MOSFET; said fourth switching circuit being switched by a control signal applied to a gate of said tenth MOSFET; (h) said equalization circuit being set in the high-impedance state, when said first switching circuit connects the other end of the channel of said first MOSFET to the first voltage line, said second switching circuit connects the other end of the channel of said second MOSFET to the second voltage line, said third switching circuit connects the other end of the channel of said third MOSFET to the first voltage line, and said fourth switching circuit connects the other end of the channel of said fourth MOSFET to the second voltage line; said first inverter circuit generating a first output signal in the second logic state at its output terminal and said second inverter circuit generating a second output signal in the first logic state at its output terminal; and (i) said equalization circuit being set in the low-impedance state, when said first switching circuit disconnects the other end of the channel of said first MOSFET from the first voltage line, said second switching circuit disconnects the other end of the channel of said second MOSFET from the second voltage line, said third switching circuit disconnects the other end of the channel of said third MOSFET from the first voltage line, and said fourth switching circuit disconnects the other end of the channel of said fourth MOSFET from the second voltage line; the output terminals of said first and second inverter circuits being connected to each other by way of said equalization circuit, resulting in the first and second output signals of said first and second inverter circuits being in an approximately medium logic state between the first and second logic states.