US 5,180,967 AGranted

Constant-current source circuit having a MOS transistor passing off-heat current

AssigneeOki Electric Industry Co., Ltd.

InventorSeiichi Yamazaki

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Abstract

There is provided a constant-current source having first current mirror circuit, connected between a first fixed voltage terminal and first and second nodes, having a first current gain; the first mirror circuit passing a first current through the first node based upon the first fixed voltage and passing a second current through the second node in accordance with the first current gain; a second current mirror circuit, connected both to the first and the second nodes, having a second current gain; the second current mirror circuit passing the second current through the second node and passing a third current in accordance with the second current gain based upon the first current passing through the first node; a current gain variation circuit, connected between the second current mirror circuit and a second fixed voltage terminal, for varying the second current gain in accordance with variation of the third current; a first activating circuit, connected between the first fixed voltage terminal and the first node, for passing a first off-leak current through the first node in accordance with the first current; a second activating circuit, connected between the second fixed voltage terminal and the second node, for passing a second off-leak current through the second node in accordance with the second current; and an output circuit, connected between an output terminal and the first fixed voltage terminal, for outputting a constant current.

Claims23

Dependent claims

A constant-current source circuit having a MOS transistor passing off-leak current comprising:

(a) a first fixed voltage terminal having a first voltage level;
(b) a second fixed voltage terminal having a second voltage level;
(c) an output terminal coupled to output a constant current;
(d) first and second nodes;
(e) a first current mirror circuit electrically coupled between the first fixed voltage terminal and said first and second nodes, and having a first current gain, said first current mirror circuit having a first current path passing a first current from said first fixed voltage terminal to said first node and a second current path passing a second current from said first fixed voltage terminal to said second node in accordance with the first current gain;
(f) a second current mirror circuit electrically coupled between the second fixed voltage terminal and said first and second nodes, and having a second current gain, said second current mirror circuit having a third current path passing a third current from said second node to said second fixed voltage terminal and a fourth current path passing a fourth current in accordance with the second current gain;
(g) a current gain variation resistor coupled between the fourth current path and said second fixed voltage terminal, for controlling the fourth current to control the second current gain;
(h) a first MOS transistor having a first conductivity type and passing a first off-leak current from said first fixed voltage terminal to said second node, the first MOS transistor including
(1) a first gate electrode to which a predetermined voltage level is applied so as to keep the first MOS transistor in the off state,
(2) a first electrode coupled to said first fixed voltage terminal, and
(3) a second electrode coupled to said second node;
and
(i) an outputting circuit coupled between the output terminal and the first fixed voltage terminal, said outputting circuit having a control terminal coupled to the first current mirror circuit, for providing the constant current to the output terminal.

10 more elements

A constant-current source circuit having a MOS transistor passing off-leak current comprising:

(a) a first fixed voltage terminal having a first voltage level;
(b) a second fixed voltage terminal having a second voltage level;
(c) an output terminal coupled to output a constant current;
(d) first and second nodes;
(e) a first current mirror circuit electrically coupled between the first fixed voltage terminal and said first and second nodes, and having a first current gain, said first current mirror circuit having a first current path passing a first current from said first fixed voltage terminal to said first node and a second current path passing a second current from said first fixed voltage terminal to said second node in accordance with the first current gain;
(f) a second current mirror circuit electrically coupled between said second fixed voltage terminal and said first and second nodes, and having a second current gain, said second current mirror circuit having a third current path passing a third current from said second node to said second fixed voltage terminal and a fourth current path passing a fourth current in accordance with the second current gain;
(g) a current gain variation resistor coupled between the fourth current path and said second fixed voltage terminal, for controlling the fourth current to control the second current gain;
(h) a first MOS transistor having a first conductivity type and passing a first off-leak current from said first node to said second fixed voltage terminal, the first MOS transistor including
(1) a first gate electrode to which a predetermined voltage level is applied so as to keep the first MOS transistor in the off state,
(2) a first electrode coupled to said first node, and
(3) a second electrode coupled to the second fixed voltage terminal;
and
(i) an outputting circuit coupled between said output terminal and the first fixed voltage terminal, said outputting circuit having a control terminal coupled to said first current mirror circuit, for providing the constant current to said output terminal.

10 more elements

A constant-current source circuit having a MOS transistor passing off-leak current comprising:

(a) a first fixed voltage terminal having a first voltage level;
(b) a second fixed voltage terminal having a second voltage level;
(c) an output terminal coupled to output a constant current;
(d) first and second nodes;
(e) a first current mirror circuit electrically coupled between the first fixed voltage terminal and said first and second nodes, and having a first current gain, the first current mirror circuit having a first current path passing a first current from said first fixed voltage terminal to said first node and a second current path passing a second current from said first fixed voltage terminal to said second node in accordance with the first current gain;
(f) a second current mirror circuit electrically coupled between said second fixed voltage terminal and said first and second nodes, and having a second current gain, said second current mirror circuit having a third current path passing a third current from said second node to said second fixed voltage terminal and a fourth current path passing a fourth current in accordance with the second current gain;
(g) a current gain variation resistor coupled between the fourth current path and said second fixed voltage terminal, for controlling the fourth current to control the second current gain;
(h) a first MOS transistor having a first conductivity type and passing a first off-leak current from said first node to said second fixed voltage terminal, the first MOS transistor including:
(1) a first gate electrode to which a predetermined voltage level is applied so as to keep said first MOS transistor in the off state,
(2) a first electrode coupled to said first node, and
(3) a second electrode coupled to said second fixed voltage terminal;
(i) a second MOS transistor having a second conductivity type and passing a second off-leak current from said first fixed voltage terminal to said first node, the second MOS transistor including:
(1) a second gate electrode to which a predetermined voltage level is applied so as to keep said second MOS transistor in the off state,
(2) a third electrode coupled to said first fixed voltage terminal, and
(3) a fourth electrode coupled to said second node;
and
(j) an outputting circuit coupled between said output terminal and said first fixed voltage terminal, the outputting circuit having a control terminal coupled to said first current mirror circuit, for providing the constant current to said output terminal.

14 more elements

Dependencies are inferred from the claim text.