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

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.