Constant current circuit

Claim 2

A constant current circuit, comprising: an output transistor having emitter, base and collector electrodes defining an emitter-base junction and an emittercollector path; a unidirectional conduction device having a semiconductur junction with matched operating characteristics to that of said emitter-base junction being connected in parallel therewith and poled to conduct in the same direction; a constant current path connected between a pair of power supply terminals and including in the order named, said emittercollector path and a load; a reference voltage device, a reference voltage terminal, and resistance means connected in a second path, in the order named, between said power supply terminals; a junction point; a current control resistor connected between said base and said junction point; and means including a semiconductor device coupling said reference voltage terminal to said junction point, the voltage across said semiconductor device varying in substantially the same manner as the voltagE across said emitter-base junction with changes in operating parameters, said current-control resistor and said emitter-base junction being connected in series between one power supply terminal and said junction point and said reference voltage device and said semiconductor device, tracking said voltage variations of said emitter-base junction, being similarly connected in series between said one power supply terminal and said junction point so that said voltage variations of said emitter-base junction are substantially cancelled and are not established across said current-control resistor.

Claim 3

The circuit recited in claim 1 further including potential switching means connected to said junction point to render said output transistor and semiconductor device concurrently conductive or non-conductive.

Claim 4

The circuit recited in claim 2 wherein said potential switching means includes a CMOS logic element having its output resistively coupled to said junction point.

Claim 5

The circuit recited in claim 1 wherein said unidirectional conduction device is a second transistor, having emitter, base and collector electrodes, being of the same conduction type as said output transistor, and having matched operating characteristics of said output transistor, said emitter of said second transistor is connected to said emitter of said output transistor, and said base and collector of said second transistor are both connected to said base of said output transistor.

Claim 6

The circuit recited in claim 1 wherein said semiconductor device is a diode.

Claim 7

The constant current circuit recited in claim 1 wherein said load includes a light emitting diode.

Claim 8

The constant current circuit recited in claim 6 wherein said light emitting diode is connected in series with a switch.

Claim 9

A circuit comprising: an output transistor having emitter, base and collector electrodes defining an emitter-base junction and an emitter-collector path; a unidirectional conduction device having a semiconductor junction with matched operating characteristics to that of said emitter-base junction being connected in parallel therewith and poled to conduct in the same direction; a constant current path connected between a pair of power supply terminals and including in the order named, said emitter-collector path, a light emitting diode and a switch; a reference voltage device, a reference voltage terminal, and resistance means connected in a second path, in the order named, between said power supply terminals; a junction point; a current control resistor connected between said base and said junction point; means including a semiconductor device coupling said reference voltage terminal to said junction point, the voltage across said semiconductor device varying in substantially the same manner as the voltage across said emitter-base junction with changes in operating parameters, said current-control resistor and said emitter-base junction being connected in series between one power supply terminal and said junction point and said reference voltage device and said semiconductor device, tracking said voltage variations of said emitter-base junction, being similarly connected in series between said one power supply terminal and said junction point so that said voltage variations of said emitter-base junction are substantially cancelled and are not established across said current-control resistor; a CMOS logic element having its output resistively coupled to said junction point to render said output transistor and semiconductor device concurrently conductive or nonconductive.

Claim 10

A circuit comprising: an output transistor having emitter, base and collector electrodes defining an emitter-base junction and an emitter-collector path; a unidirectional conduction device having a semiconductor junction with matched operating characteristics to that of said emitter-base junction being connected in parallel therewith and poled to conduct in the same direction; a constant current path connected between a pair of power supply terminals and including in the order named, said emitter-collector path, a light emitting diode and a switch; a reference voltage device, a reference voltage terminal, and resistance means connected in a second path, in the order named, between said power supply terminals; a junction point; a current control resistor connected between said base and said junction point; means including a semiconductor device coupling said reference voltage terminal to said junction point, the voltage across said semiconductor device varying in substantially the same manner as the voltage across said emitter-base junction with changes in operating parameters, said current-control resistor and said emitter-base junction being connected in series between one power supply terminal and said junction point and said reference voltage device and said semiconductor device, tracking said voltage variations of said emitter-base junction, being similarly connected in series between said one power supply terminal and said junction point so that said voltage variations of said emitter-base junction are substantially cancelled and are not established across said current-control resistor; a CMOS logic element having its output resistively coupled to said junction point to render said output transistor and semiconductor device concurrently conductive or nonconductive.

Claim 11

A constant current circuit comprising: an output transistor having emitter, base and collector electrodes defining an emitter-base junction and an emitter-collector path; a load connected in a constant current path with said emitter-collector path between a pair of power supply terminals; a reference voltage device, a reference voltage terminal and resistance meaNs connected in a second path between said power supply terminals; a junction point; a current control resistor connected in series with said emitter-base junction between said junction point and one of said power supply terminals; means including a semiconductor device coupling said reference voltage terminal to said junction point, the voltage across said semiconductor device varying in substantially the same manner as the voltage across said emitter-base junction with changes in operating parameters, said current-control resistor and said emitter-base junction being connected in series between one power supply terminal and said junction point and said reference voltage device and said semiconductor device, tracking said voltage variations of said emitter-base junction, being similarly connected in series between said one power supply terminal and said junction point so that said voltage variations of said emitter-base junction are substantially cancelled and do not appear across said current-control resistor; and potential switching means connected to said junction point to render said output transistor and said semiconductor device concurrently conductive or nonconductive.

Claim 12

A constant current circuit comprising: an output transistor having emitter, base and collector electrodes defining an emitter-base junction and an emitter-collector path; a load connected in a constant current path with said emitter-collector path between a pair of power supply terminals; a reference voltage device, a reference voltage terminal and resistance meaNs connected in a second path between said power supply terminals; a junction point; a current control resistor connected in series with said emitter-base junction between said junction point and one of said power supply terminals; means including a semiconductor device coupling said reference voltage terminal to said junction point, the voltage across said semiconductor device varying in substantially the same manner as the voltage across said emitter-base junction with changes in operating parameters, said current-control resistor and said emitter-base junction being connected in series between one power supply terminal and said junction point and said reference voltage device and said semiconductor device, tracking said voltage variations of said emitter-base junction, being similarly connected in series between said one power supply terminal and said junction point so that said voltage variations of said emitter-base junction are substantially cancelled and do not appear across said current-control resistor; and potential switching means connected to said junction point to render said output transistor and said semiconductor device concurrently conductive or nonconductive.

Claim 13

The constant current circuit recited in claim 9 wherein said current-control resistor is connected between said power supply terminal and said emitter of said output transistor, said load is connected to said collector of said output transistor, and said junction point is connected to said base of said output transistor.

Claim 14

The constant current circuit recited in claim 9 wherein said load includes a light emitting diode.

Claim 15

The constant current circuit recited in claim 11 wherein said light emitting diode is connected in series with a switch.

Claim 16

The constant current circuit recited in claim 9 wherein said semiconductor device is a second transistor having emitter, base and collector electrodes but being of conductivity type opposite that of said ouput transistor, said emitter and base electrodes defining the ends of an emitter-base junction has a semiconductor voltage drop which, during conduction, varies in substantially the same manner as the voltage across said emitter-base junction of said output transistor varies with changes in operating parameters, said base of said second transistor is connected to said reference voltage terminal, said emitter of said second transistor is connected to said junction point, and said collector is coupled to a power supply terminal.

Claim 17

The constant-current circuit recited in claim 13 wherein said output transistor and said second transistor have matched operating characteristics.

Claim 18

The constant-current circuit recited in claim 9 wherein said semiconductor device is a diode.

Claim 19

The circuit recited in claim 9 wherein said potential switching means includes a CMOS logic element having its output resistively coupled to said junction point.

Claim 20

A circuit comprising: an output transistor having emitter, base and collector electrodes defining an emitter base junction and an emitter-collector path; a load including a light emitting diode connected in series with a switch connected in a constant current path with said emitter-collector path between a pair of power supply terminals; a reference voltage device, a reference voltage terminal and resistance means connected in a second path between said power supply terminals; a junction point; a current control resistor connected in series with said emitter-base junction between said junction point and one of said power supply terminals; means including a semiconductor device coupling said reference voltage terminal to said junction point, the voltage across said semiconductor device varying in substantially the same manner as the voltage across said emitter-base junction with changes in operating parameters, said current-control resistor and said emitter-base junction being connected in series between one power supply terminal and said junction point and said reference voltage device and said semiconductor device, tracking said voltage variations of said emitter-base junction, being similarly connected in series between said one power supply terminal and said junction point so that said voltage variations of said emitter-base junction are substantially cancelled and do not appear across said current-control resistor; and a CMOS logic element having its output resistively coupled to said junction point to render said output transistor and said semiconductor device concurrently conductive or nonconductive.

Claim 21

A circuit comprising: an output transistor having emitter, base and collector electrodes defining an emitter base junction and an emitter-collector path; a load including a light emitting diode connected in series with a switch connected in a constant current path with said emitter-collector path between a pair of power supply terminals; a reference voltage device, a reference voltage terminal and resistance means connected in a second path between said power supply terminals; a junction point; a current control resistor connected in series with said emitter-base junction between said junction point and one of said power supply terminals; means including a semiconductor device coupling said reference voltage terminal to said junction point, the voltage across said semiconductor device varying in substantially the same manner as the voltage across said emitter-base junction with changes in operating parameters, said current-control resistor and said emitter-base junction being connected in series between one power supply terminal and said junction point and said reference voltage device and said semiconductor device, tracking said voltage variations of said emitter-base junction, being similarly connected in series between said one power supply terminal and said junction point so that said voltage variations of said emitter-base junction are substantially cancelled and do not appear across said current-control resistor; and a CMOS logic element having its output resistively coupled to said junction point to render said output transistor and said semiconductor device concurrently conductive or nonconductive.