Differential amplifier circuit using quadritail circuit

Claim 2

A differential amplifier circuit comprising: a quadritail circuit and a differential circuit; said quadritail circuit including a first transistor pair of first and second MOS transistors, a second transistor pair of third and fourth MOS transistors, and a constant current source for driving said first and second transistor pairs; drains of said first and second transistors being connected in common, drains of said third and fourth transistors being connected in common, and sources of said first to fourth transistors being connected in common to said constant current source; and said differential pair being composed of fifth and sixth MOS transistors and being driven by a current twice in value as much as an output current of said quadritail circuit; wherein an input voltage is differentially applied between gates of said first and second transistors and between gates of said fifth and sixth transistors, respectively; a DC voltage is applied to common-connected gates of said third and fourth transistors of said second transistor pair; and an output current being derived from an output end of said differential pair.

Claim 3

A differential amplifier circuit as claimed in claim 1, further comprising: a first resistor connected between said gates of said third and fourth transistors and said gate of said first transistor; and a second resistor connected between said gates of said third and fourth transistors and said gate of said second transistor; wherein said DC voltage is generated by using said first and second resistors.

Claim 4

A differential amplifier circuit as claimed in claim 1 or 2, further comprising: a seventh MOS transistor which is driven by said output current of said quadritail circuit, and eighth and ninth MOS transistors connected in parallel and driven by said seventh MOS transistor, said eighth and ninth MOS transistors having transconductances equal to each other; wherein and said driving current for said differential pair is generated by said eighth and ninth MOS transistors.

Claim 5

A differential amplifier circuit comprising: a quadritail circuit and a differential circuit; said quadritail circuit including a first transistor pair of first and second MOS transistors, a second transistor pair of third and fourth MOS transistors, and a first constant current source for driving said first and second transistor pairs; drains of said first and second transistors being connected in common, drains of said third and fourth transistors being connected in common, and sources of said first to fourth transistors being connected in common to said constant current source; and said differential pair being composed of fifth and sixth MOS transistors and being driven by a current equal in value to sum of said current of said constant current source and said output current of said quadritail circuit; wherein an input voltage is differentially applied between gates of said first and second transistors and between gates of said fifth and sixth transistors, respectively; a DC voltage is applied to common-connected gates of said third and fourth transistors of said second transistor pair; and an output current being derived from an output end of said differential pair.

Claim 6

A differential amplifier circuit comprising: a quadritail circuit and a differential circuit; said quadritail circuit including a first transistor pair of first and second MOS transistors, a second transistor pair of third and fourth MOS transistors, and a first constant current source for driving said first and second transistor pairs; drains of said first and second transistors being connected in common, drains of said third and fourth transistors being connected in common, and sources of said first to fourth transistors being connected in common to said constant current source; and said differential pair being composed of fifth and sixth MOS transistors and being driven by a current equal in value to sum of said current of said constant current source and said output current of said quadritail circuit; wherein an input voltage is differentially applied between gates of said first and second transistors and between gates of said fifth and sixth transistors, respectively; a DC voltage is applied to common-connected gates of said third and fourth transistors of said second transistor pair; and an output current being derived from an output end of said differential pair.

Claim 7

A differential amplifier circuit as claimed in claim 4, further comprising: a first resistor connected between said gates of said third and fourth transistors and said gate of said first transistor; and a second resistor connected between said gates of said third and fourth transistors and said gate of said second transistor; wherein said middle point voltage is generated by using said first and second resistors.

Claim 8

A differential amplifier circuit as claimed in claim 4 or 5, further comprising: a seventh MOS transistor which is driven by said output current of said quadritail circuit, and an eighth MOS transistor and a second constant current source connected in parallel for generating said driving current of said differential pair; wherein said eighth MOS transistor and said second constant current source are connected to common-connected sources of said fifth and sixth transistors of said differential pair, and said second constant current source generates a constant current equal in value to that of said first constant current source.

Claim 9

A differential amplifier circuit as claimed in claim 6, further comprising a current mirror circuit composed of MOS transistors acting as an active load of said quadritail circuit, said output current of said quadritail circuit is derived through said current mirror circuit.

Claim 10

A differential amplifier circuit comprising: a quadritail circuit including a first transistor pair of first and second MOS transistors, a second transistor pair of third and fourth MOS transistors, and a first constant current source for driving said first and second transistor pairs; drains of said first and second transistors being connected in common, drains of said third and fourth transistors being connected in common, and sources of said first to fourth transistors being connected in common to said first constant current source; a second constant current source connected to said common-connected drains of said first and second transistors; a differential pair composed of fifth and sixth MOS transistors; a third constant current source for driving said differential pair, said third constant current source being connected to said common-connected drains of said first and second transistors; and a current level shifter for shifting a current level between said common-connected drains of said first and second transistors and those of said fifth and sixth transistors; wherein an input voltage is differentially applied between gates of said first and second transistors and between gates of said fifth and sixth transistors, respectively; a DC voltage is applied to common-connected gates of said third and fourth transistors of said second transistor pair; and an output current being derived from an output end of said differential pair.

Claim 11

A differential amplifier circuit comprising: a quadritail circuit including a first transistor pair of first and second MOS transistors, a second transistor pair of third and fourth MOS transistors, and a first constant current source for driving said first and second transistor pairs; drains of said first and second transistors being connected in common, drains of said third and fourth transistors being connected in common, and sources of said first to fourth transistors being connected in common to said first constant current source; a second constant current source connected to said common-connected drains of said first and second transistors; a differential pair composed of fifth and sixth MOS transistors; a third constant current source for driving said differential pair, said third constant current source being connected to said common-connected drains of said first and second transistors; and a current level shifter for shifting a current level between said common-connected drains of said first and second transistors and those of said fifth and sixth transistors; wherein an input voltage is differentially applied between gates of said first and second transistors and between gates of said fifth and sixth transistors, respectively; a DC voltage is applied to common-connected gates of said third and fourth transistors of said second transistor pair; and an output current being derived from an output end of said differential pair.

Claim 12

A differential amplifier circuit as claimed in claim 8, further comprising: a first resistor connected between said gates of said third and fourth transistors and said gate of said first transistor; and a second resistor connected between said gates of said third and fourth transistors and said gate of said second transistor; wherein said middle point voltage is generated by using said first and second resistors.

Claim 13

A differential amplifier circuit as claimed in claim 9, further comprising a current mirror circuit composed of MOS transistors acting as an active load of said quadritail circuit, said output current of said quadritail circuit is derived through said current mirror circuit.

Claim 14

A differential amplifier circuit as claimed in claim 8 or 10, wherein a constant current of said first constant current source is l o , and those of said second and third constant current sources are bl o and cl o , respectively, where b and c are constants, and said constants b and c satisfy relationships of b 1 and c - b 0.

Claim 15

A differential amplifier circuit as claimed in claim 11, wherein b = 1 and c = 2.

Claim 16

A differential amplifier circuit comprising: a quadritail circuit and a differential circuit; said quadritail circuit including a first transistor pair of first and second MOS transistors, a second transistor pair of third and fourth MOS transistors, and a first constant current source for driving said first and second transistor pairs; drains of said first and second transistors being connected in common, drains of said third and fourth transistors being connected in common, and sources of said first to fourth transistors being connected in common to said constant current source; and said differential pair being composed of fifth and sixth MOS transistors and being driven by a current equal in value to said output current of said quadritail circuit; wherein an input voltage is differentially applied between gates of said fifth and sixth transistors and a voltage obtained by changing a voltage level of said input voltage is applied between said gates of the first and second transistors; a DC generated from said level-changed voltage is applied to common-connected gates of said third and fourth transistors of said second transistor pair; and an output current being derived from an output end of said differential pair.

Claim 17

A differential amplifier circuit comprising: a quadritail circuit and a differential circuit; said quadritail circuit including a first transistor pair of first and second MOS transistors, a second transistor pair of third and fourth MOS transistors, and a first constant current source for driving said first and second transistor pairs; drains of said first and second transistors being connected in common, drains of said third and fourth transistors being connected in common, and sources of said first to fourth transistors being connected in common to said constant current source; and said differential pair being composed of fifth and sixth MOS transistors and being driven by a current equal in value to said output current of said quadritail circuit; wherein an input voltage is differentially applied between gates of said fifth and sixth transistors and a voltage obtained by changing a voltage level of said input voltage is applied between said gates of the first and second transistors; a DC generated from said level-changed voltage is applied to common-connected gates of said third and fourth transistors of said second transistor pair; and an output current being derived from an output end of said differential pair.

Claim 18

A differential amplifier circuit comprising: a quadritail circuit and a differential circuit; said quadritail circuit including a first transistor pair of first and second MOS transistors, a second transistor pair of third and fourth MOS transistors, and a first constant current source for driving said first and second transistor pairs; drains of said first and second transistors being connected in common, drains of said third and fourth transistors being connected in common, and sources of said first to fourth transistors being connected in common to said constant current source; and said differential pair being composed of fifth and sixth MOS transistors and being driven by a current equal in value to said output current of said quadritail circuit; wherein an input voltage is differentially applied between gates of said first and second transistors and a voltage obtained by changing a voltage level of said input voltage is applied between said gates of the fifth and sixth transistors; a DC voltage generated from said input voltage is applied to common-connected gates of said third and fourth transistors of said second transistor pair; and an output current being derived from an output end of said differential pair.

Claim 19

A differential amplifier circuit comprising: a quadritail circuit and a differential circuit; said quadritail circuit including a first transistor pair of first and second MOS transistors, a second transistor pair of third and fourth MOS transistors, and a first constant current source for driving said first and second transistor pairs; drains of said first and second transistors being connected in common, drains of said third and fourth transistors being connected in common, and sources of said first to fourth transistors being connected in common to said constant current source; and said differential pair being composed of fifth and sixth MOS transistors and being driven by a current equal in value to said output current of said quadritail circuit; wherein an input voltage is differentially applied between gates of said first and second transistors and a voltage obtained by changing a voltage level of said input voltage is applied between said gates of the fifth and sixth transistors; a DC voltage generated from said input voltage is applied to common-connected gates of said third and fourth transistors of said second transistor pair; and an output current being derived from an output end of said differential pair.

Claim 20

A differential amplifier circuit as claimed in claim 13 or 14, further comprising: a first resistor connected between said gates of said third and fourth transistors and said gate of said first transistor; and a second resistor connected between said gates of said third and fourth transistors and said gate of said second transistor; wherein said DC voltage is generated by using said first and second resistors.

Claim 21

A differential amplifier circuit as claimed in claim 13, 14 or 15, wherein transconductance parameters of said fifth and sixth transistors are different from those of said first to fourth transistors.