Constant current source circuit

Claim 2

A constant current source circuit comprising: a current mirror circuit supplying a load circuit with an output current which is regulated on the basis of a reference current; a transistor having an emitter, a collector connected to a first power source line, and a base coupled to said current mirror circuit; a resistor coupled between said emitter and base, said reference current passing through said resistor; current control means, coupled to said emitter, for controlling a current directed to a second power source line in accordance with a bias voltage, said current composed of said reference current and a collector current passing through said transistor; and bias means, coupled to said current control means and having a current path, for deriving said bias voltage from a current passing from said first power source line to said second power source line through said current path.

Claim 3

A constant current source circuit as claimed in claim 1, wherein said current control means comprises a metal-oxide-semiconductor (MOS) transistor coupled between the emitter of said transistor and said second power source line, and said MOS transistor has a gate to which said bias voltage supplied from said bias means is applied.

Claim 4

A constant current source circuit as claimed in claim 1, wherein said bias means comprises a resistor having a first terminal coupled to said first power source line and a second terminal, and an n-channel MOS transistor having a drain coupled to the second terminal of said resistor, a gate coupled to said drain, and a source coupled to said second power source line, and wherein said bias voltage is drawn from the gate of said n-channel MOS transistor.

Claim 5

A constant current source circuit as claimed in claim 1, wherein said bias means comprises a p-channel MOS transistor having a source coupled to said first power source line, a gate, and a drain coupled to said gate, and an n-channel MOS transistor having a drain coupled to the gate and drain of said p-channel MOS transistor, a gate coupled to the drain thereof, and a source coupled to said second power source line, and wherein said bias voltage is drawn from the gate of said n-channel MOS transistor.

Claim 6

A constant current source circuit as claimed in claim 1, wherein said bias means comprises a first n-channel MOS transistor having a drain coupled to said first power source line, a gate coupled to said drain thereof, and a source, and a second n-channel MOS transistor having a drain coupled to the source of said first n-channel MOS transistor, a gate coupled to said drain thereof, and a source coupled to said second power source line, and wherein said bias voltage is drawn from the gate of said second n-channel MOS transistor.

Claim 7

A constant current source circuit as claimed in claim 1, wherein said bias means comprises a depletion type MOS transistor.

Claim 8

A constant current source circuit as claimed in claim 3, wherein said resistor comprises a diffusion resistor.

Claim 9

A constant current source circuit as claimed in claim 3, wherein said resistor comprises a polysilicon resistor.

Claim 10

A constant current source circuit as claimed in claim 1, wherein said transistor is an npn-type bipolar transistor.

Claim 11

A constant current source as claimed in claim 1, wherein said first and second power source lines receive a power source voltage from a battery.

Claim 12

A constant current source circuit as claimed in claim 1, wherein said load circuit comprises a MOS transistor having a drain coupled to said current mirror circuit, a source coupled to said second power source line, and a gate coupled to said drain.

Claim 13

A constant current source circuit comprising: a current mirror circuit supplying a load circuit with an output current which is regulated on the basis of a first reference current; a transistor having an emitter, a collector connected to a first power source line, and a base coupled to said current mirror circuit; a resistor coupled between said emitter and base, said first reference current passing through said resistor; and current mirror means, coupled to the emitter of said transistor, for controlling a current directed to a second power source line in accordance with a second reference current, said current composed of said second reference current and a collector current passing through said transistor, and said second reference current being directed from said first power source line to said second power source line; wherein the second reference current flows to the second power source line from the first power source line through a current path which is different from current paths through which the output current and the first reference current respectively pass.

Claim 14

A constant current source circuit comprising: a current mirror circuit supplying a load circuit with an output current which is regulated on the basis of a first reference current; a transistor having an emitter, a collector connected to a first power source line, and a base coupled to said current mirror circuit; a resistor coupled between said emitter and base, said first reference current passing through said resistor; and current mirror means, coupled to the emitter of said transistor, for controlling a current directed to a second power source line in accordance with a second reference current, said current composed of said second reference current and a collector current passing through said transistor, and said second reference current being directed from said first power source line to said second power source line; wherein the second reference current flows to the second power source line from the first power source line through a current path which is different from current paths through which the output current and the first reference current respectively pass.

Claim 15

A constant current source circuit as claimed in claim 12, wherein said current mirror means comprises voltage drop means for deriving a voltage drop from said second reference current, and a pair of transistors which are connected so as to configure a current mirror circuit, and wherein said second reference current passes through one of said pair of transistors, and said current passes through the other of said pair of transistors.

Claim 16

A constant current source circuit as claimed in claim 13, wherein said pair of transistors are MOS transistors.

Claim 17

A constant current source circuit as claimed in claim 13, wherein said pair of transistors are bipolar transistors.

Claim 18

A constant current source circuit as claimed in claim 13, wherein said voltage drop means comprises a resistor.

Claim 19

A constant current source circuit as claimed in claim 12, wherein said first and second power source lines receive a power source voltage from a battery.

Claim 20

A constant current source circuit as claimed in claim 12, wherein said load circuit comprises a MOS transistor having a drain coupled to said current mirror circuit, a source coupled to said second power source line, and a gate coupled to said drain.

Claim 21

A constant current source circuit adapted to a differential amplifier circuit including first and second transistors having sources mutually connected so as to configure a differential circuit and including a third transistor which is coupled between said sources and a first power source line and passes a current from said sources to said first power source line, said third transistor having a gate coupled to said constant current source circuit, said constant current source circuit comprising: a current mirror circuit supplying a load circuit with an output current which is regulated on the basis of a reference current; a transistor having an emitter, a collector connected to a second power source line, and a base coupled to said current mirror circuit; a resistor coupled between said emitter and base, said reference current passing through said resistor; current control means, coupled to said emitter, for controlling a current directed to said first power source line in accordance with a bias voltage, said current composed of said reference current and a collector current passing through said transistor; and bias means, coupled to said current control means and having a current path, for deriving said bias voltage from a current passing from said second power source line to said first power source line through said current path.

Claim 22

A constant current source circuit adapted to a differential amplifier circuit including first and second transistors having sources mutually connected so as to configure a differential circuit and including a third transistor which is coupled between said sources and a first power source line and passes a current from said sources to said first power source line, said third transistor having a gate coupled to said constant current source circuit, said constant current source circuit comprising: a current mirror circuit supplying a load circuit with an output current which is regulated on the basis of a reference current; a transistor having an emitter, a collector connected to a second power source line, and a base coupled to said current mirror circuit; a resistor coupled between said emitter and base, said reference current passing through said resistor; current control means, coupled to said emitter, for controlling a current directed to said first power source line in accordance with a bias voltage, said current composed of said reference current and a collector current passing through said transistor; and bias means, coupled to said current control means and having a current path, for deriving said bias voltage from a current passing from said second power source line to said first power source line through said current path.