US3777251A - Constant current regulating circuit - Google Patents

Constant current regulating circuit Download PDF

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Publication number
US3777251A
US3777251A US00294723A US3777251DA US3777251A US 3777251 A US3777251 A US 3777251A US 00294723 A US00294723 A US 00294723A US 3777251D A US3777251D A US 3777251DA US 3777251 A US3777251 A US 3777251A
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United States
Prior art keywords
current
transistor
control electrode
semiconductive device
output
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Expired - Lifetime
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US00294723A
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English (en)
Inventor
J Cecil
W Davis
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Motorola Solutions Inc
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Motorola Inc
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Publication date
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F3/00—Non-retroactive systems for regulating electric variables by using an uncontrolled element, or an uncontrolled combination of elements, such element or such combination having self-regulating properties
    • G05F3/02—Regulating voltage or current
    • G05F3/08—Regulating voltage or current wherein the variable is dc
    • G05F3/10—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics
    • G05F3/16—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices
    • G05F3/20—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations
    • G05F3/22—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations wherein the transistors are of the bipolar type only
    • G05F3/222—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations wherein the transistors are of the bipolar type only with compensation for device parameters, e.g. Early effect, gain, manufacturing process, or external variations, e.g. temperature, loading, supply voltage
    • G05F3/227—Regulating voltage or current wherein the variable is dc using uncontrolled devices with non-linear characteristics being semiconductor devices using diode- transistor combinations wherein the transistors are of the bipolar type only with compensation for device parameters, e.g. Early effect, gain, manufacturing process, or external variations, e.g. temperature, loading, supply voltage producing a current or voltage as a predetermined function of the supply voltage

Definitions

  • v ABSTRACT Circuitry for providing a constant current to a load includes a source of current and a regulating circuit interposed between the current source and the load.
  • the regulating circuit includes a current shunting transistor coupled to the output of the current source and a feedback transistor also coupled to the output of the current source and to the base of the current shunting transistor.
  • a diode connected between the current shunting transistor and the current source is chosen to have a dynamic admittance substantially equal to the transconductance of the current shunting transistor to provide the latter with unity voltage gain.
  • a variation in current output of the source is accommodated by the current shunting transistor so that a substantially constant voltage at the output thereof is maintained.
  • An output circuit including a transistor, coupled to the output of the current shunting transistor and to the load, and controlled by the output voltage, provides a substantially constant current to the load despite current variations from the current 9 Claims, 1 Drawing Figure 52 us. c1. 323/4, 323/22 T 51 Int. Cl. G05f 3/08 [58] Field 61 Search 323/4,9, 22 T, 1; 307/296, 297
  • This invention relates generally .to circuitry for providing a constant current output .and more particularly to circuitry for regulating such constant current producing circuitry.
  • the current from the constant current source varies,.sometimes because of a variation in the voltage powering the constant current source.
  • the operation of the load can be greatly affected. This is especially true when the current produced is being used for biasing circuitry in the operational amplifier.
  • Regulating circuits which attempt to maintain the current to the load constant are known in the prior art. These circuits, however, are often sensitive to changes in the constant current source and therefore introduce such things as poor power supply sensitivity which in turn affects the current to the load.
  • a preferred embodiment of the constant current regulating circuitry comprises a first transistor coupled at the. collector thereof to the cathode of a diode and a feedback arrangement including a second transistor, the base of ample, a field effect transistor (FET) appropriately connected, is coupled to the anode of the diode and base of the second (feedback) transistor.
  • FET field effect transistor
  • Any variation in the current through the FET due to variations in the power supply powering the latter or due to fabrication variations which may cause the FET current to vary from unit to unit, are compensated for by the action of the current regulating circuitry.
  • the firstmentioned transistor shunts varying amounts of current, and maintains a substantially constant voltage at the output thereof, to in turn maintain a substantially constant current flow through the third transistor to the load.
  • FIGURE of the drawing is a schematic diagram of a preferred embodiment of the constant current regulating circuitry according to the invention.
  • the current regulating circuitry 10 is coupled at the input 12 thereof to the output 13 of a commonly used constant current source 14, herein taking the form of a field effect transistor (FET) connected to produce a constant current output.
  • the PET is powered from a first voltage source or power supply (not shown) connected at point 16. While a constant current source has been illustrated herein and is preferred, the current regulating circuit 10 according to the invention is operable also wherein the FET is replaced by a resistor or like component.
  • the output 18 of the current regulating circuit 10 is coupled via lead 22 to a load 20.
  • the load is also connected to a voltage source at point 24, normally differentthan that powering the FET.
  • the current regulating circuitry 10 includes a diode 26, the anode or input electrode 28 of which is coupled to the constant current source (FET) 14.
  • the cathode 30 of the diode is connected to the collector 32 of a transistor 34.
  • a second transistor 36 forming a feedback stage, is connected at the base 38 thereof to the output 13 of the FET circuit source and to the anode of diode 26.
  • the collector 40 of transistor 36 is connected via lead 39 to the junction 16 and the power supply (not shown) supplying the constant current source 14.
  • the emitter 42 of transistor 36 is connected over lead 44 to the base 46 of transistor 34, as well as to ground through a resistor 48.
  • the emitter 50 of transistor 34 is grounded as well.
  • An output stage 52 of the current regulating circuit I includes a transistor 54, the base 56 of which is connected to the output (collector) 32 of transistor 34.
  • the collector or output electrode 58 of the transistor 54 is connected to the load 20 at junction 18 and the emitter 60 of the transistor 54 is connected to ground through a resistor 62.
  • the dynamic admittance of the diode 26 is substantially equal to the transconductance of transistor 34. It should be noted that the gain of a transistor is equal to the transconductance thereof multiplied by the load resistance or the transconductance divided by the admittance of the load. The transistor thus exhibits a voltage amplification of one or unity gain when the admittance of the diode is equal to. the transconductance of the transistor. In operation, ragardless of the current flowing from the current source FET 14, the voltage supplied to the base of transistor 54 is maintained substantially constant.
  • Transistor 36 in the feedback path, adjusts the cur rent shunted by transistor 34 thereby maintaining the voltage at junction 64 substantially constant regardless of changes in the supply voltage or variations in the FET.
  • the voltage at point 64 may vary with temperature and/or resistor variations. This variation in voltage at junction 64 due to temperature, however, compensates for changes in the base-emitter voltage of transistor 54, thus producing a constant current at collector 58 thereof.
  • load 20 comprises circuitry in an operational amplifier, requiring biasing with a constant reference current.
  • the regulating circuitry of the invention With the regulating circuitry of the invention, the latter is insured. Any variation in the current derived from the constant current source 14 is compensated for by the regulating circuitry, as described, to maintain the current at lead 22 substantially constant.
  • the regulating circuitry 10 which includes only three transistors anda diode, can be easily fabricated as an integrated circuit.
  • a P-N semiconductive junction device connected to the current source, and oriented to pass current to the junction point;
  • a current shunting semiconductive device having a first main electrode connected to the junction point, a second main electrode connected to a common reference point, and a control electrode, the dynamic electrical characteristics of the current shunting semiconductor device and the P-N junction semiconductive device being equal for providing the former with unity gain;
  • feedback circuit means connected to the connection between the current source and the P-N junction semiconductive device and the control electrode of the current shunting semiconductive device for providing the latter with signals representative of changes in current supplied by the current source for maintaining the junction point at a constant voltage;
  • output circuit means connected to the load and to the junction point, responsive to the voltage at the junction point, for providing constant current to the load.
  • the feedback circuit means further comprise a semiconductive device having a first main electrode connected to the reference potential, a control electrode connected to the connection between the current source and the semiconductive junction device, and a second main electrode connected to the control electrode of the current shunting semiconductive device.
  • the output circuit means further comprises a semiconductive device having a first main electrode connected to the load, a second main electrode electrically coupled to the common reference point and a control electrode electrically connected to,the junction point.
  • the current shunting semiconductive device is a transistor, the collector and emitter thereof being the first and second main electrodes and the base being the control electrode, and wherein the P-N junction semiconductive device is a diode whose dynamic admittance is substantially equal to the transconductance of the current shunting transistor.
  • the regulating circuitry of claim 2 wherein the feedback semiconductive device is a transistor whose collector and emitter are the first and second main electrodes and whose base is the control electrode.
  • the regulating circuitry of claim 3 wherein the output circuit semiconductive device is a transistor whose collector and emitter are the first and second main electrodes and whose base is the control electrode.
  • the feedback semiconductive device is a transistor whose collector and emitter are the first and second main electrodes and whose base is the control electrode.
  • the output circuit semiconductive device is a transistor whose collector and emitter are the first and second main electrodes and whose base is the control electrode.
  • circuitry of the type claimed in claim 8 wherein said constant current source comprises a field effect transistor connected to provide a relatively constant current output.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Control Of Electrical Variables (AREA)
  • Continuous-Control Power Sources That Use Transistors (AREA)
  • Amplifiers (AREA)
US00294723A 1972-10-03 1972-10-03 Constant current regulating circuit Expired - Lifetime US3777251A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US29472372A 1972-10-03 1972-10-03

Publications (1)

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US3777251A true US3777251A (en) 1973-12-04

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Application Number Title Priority Date Filing Date
US00294723A Expired - Lifetime US3777251A (en) 1972-10-03 1972-10-03 Constant current regulating circuit

Country Status (5)

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US (1) US3777251A (it)
JP (1) JPS5414750B2 (it)
DE (1) DE2349462C3 (it)
FR (1) FR2201578B1 (it)
GB (1) GB1396669A (it)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3886435A (en) * 1973-08-03 1975-05-27 Rca Corp V' be 'voltage voltage source temperature compensation network
US3900790A (en) * 1972-06-06 1975-08-19 Sony Corp Constant current circuit
US3932803A (en) * 1973-06-14 1976-01-13 Robert Buck Electronic monitoring system including contactless motion detector
US4009432A (en) * 1975-09-04 1977-02-22 Rca Corporation Constant current supply
US4177417A (en) * 1978-03-02 1979-12-04 Motorola, Inc. Reference circuit for providing a plurality of regulated currents having desired temperature characteristics
EP0115003A1 (en) * 1982-12-27 1984-08-08 Motorola, Inc. Current source

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS52161321U (it) * 1976-05-31 1977-12-07
DE10205194A1 (de) * 2002-02-08 2003-08-28 Tyco Electronics Amp Gmbh Schaltungsanordnung zur Steuerung eines konstanten Stromes durch eine Last

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB990309A (en) * 1963-05-01 1965-04-28 Atomic Energy Authority Uk Improvements in or relating to electric circuits for matching high impedance signal sources to low impedance loads
US3303413A (en) * 1963-08-15 1967-02-07 Motorola Inc Current regulator
US3588672A (en) * 1968-02-08 1971-06-28 Tektronix Inc Current regulator controlled by voltage across semiconductor junction device
US3629692A (en) * 1971-01-11 1971-12-21 Rca Corp Current source with positive feedback current repeater
US3648153A (en) * 1970-11-04 1972-03-07 Rca Corp Reference voltage source
US3681623A (en) * 1968-03-15 1972-08-01 Ibm Geometric current amplifier

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3383612A (en) * 1965-11-29 1968-05-14 Rca Corp Integrated circuit biasing arrangements
US3430155A (en) * 1965-11-29 1969-02-25 Rca Corp Integrated circuit biasing arrangement for supplying vbe bias voltages
US3532981A (en) * 1968-01-15 1970-10-06 Ford Motor Co Constant current instrument regulator
DE1300149B (de) * 1968-05-02 1969-07-31 Itt Ind Gmbh Deutsche Integrierte Halbleiterfestkoerperschaltung fuer einen Transistor-Schaltverstaerker, insbesondere zur Anwendung bei sich selbst steuernden Uhrenantrieben

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB990309A (en) * 1963-05-01 1965-04-28 Atomic Energy Authority Uk Improvements in or relating to electric circuits for matching high impedance signal sources to low impedance loads
US3303413A (en) * 1963-08-15 1967-02-07 Motorola Inc Current regulator
US3588672A (en) * 1968-02-08 1971-06-28 Tektronix Inc Current regulator controlled by voltage across semiconductor junction device
US3681623A (en) * 1968-03-15 1972-08-01 Ibm Geometric current amplifier
US3648153A (en) * 1970-11-04 1972-03-07 Rca Corp Reference voltage source
US3629692A (en) * 1971-01-11 1971-12-21 Rca Corp Current source with positive feedback current repeater

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3900790A (en) * 1972-06-06 1975-08-19 Sony Corp Constant current circuit
US3932803A (en) * 1973-06-14 1976-01-13 Robert Buck Electronic monitoring system including contactless motion detector
US3886435A (en) * 1973-08-03 1975-05-27 Rca Corp V' be 'voltage voltage source temperature compensation network
US4009432A (en) * 1975-09-04 1977-02-22 Rca Corporation Constant current supply
US4177417A (en) * 1978-03-02 1979-12-04 Motorola, Inc. Reference circuit for providing a plurality of regulated currents having desired temperature characteristics
EP0115003A1 (en) * 1982-12-27 1984-08-08 Motorola, Inc. Current source

Also Published As

Publication number Publication date
JPS5414750B2 (it) 1979-06-09
FR2201578A1 (it) 1974-04-26
DE2349462A1 (de) 1974-04-11
FR2201578B1 (it) 1977-05-27
GB1396669A (en) 1975-06-04
DE2349462C3 (de) 1981-06-11
DE2349462B2 (de) 1977-03-03
JPS4972646A (it) 1974-07-13

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