WO1979000295A1 - Sources de courant - Google Patents

Sources de courant Download PDF

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Publication number
WO1979000295A1
WO1979000295A1 PCT/GB1978/000041 GB7800041W WO7900295A1 WO 1979000295 A1 WO1979000295 A1 WO 1979000295A1 GB 7800041 W GB7800041 W GB 7800041W WO 7900295 A1 WO7900295 A1 WO 7900295A1
Authority
WO
WIPO (PCT)
Prior art keywords
input
signal
current
output
amplifier
Prior art date
Application number
PCT/GB1978/000041
Other languages
English (en)
Inventor
D Shobbrook
Original Assignee
Gen Electric Co Ltd
D Shobbrook
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Gen Electric Co Ltd, D Shobbrook filed Critical Gen Electric Co Ltd
Priority to DE19782857168 priority Critical patent/DE2857168A1/de
Publication of WO1979000295A1 publication Critical patent/WO1979000295A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/60—Substation equipment, e.g. for use by subscribers including speech amplifiers
    • H04M1/6025—Substation equipment, e.g. for use by subscribers including speech amplifiers implemented as integrated speech networks
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/10—Regulating voltage or current
    • G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
    • G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
    • G05F1/561—Voltage to current converters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/08—Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements
    • H03F1/083—Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements in transistor amplifiers

Definitions

  • This invention relates to current scarcer and in particular to such current sources in which the magnitude of the output current of the source is determined by the magnitude of a control voltage.
  • Conventional current sources which are designed to produce an output current whose magnitude is a function of an input signal to the source, are frequently provided with a negative feedback loop whose function it is to keep the output current as nearly as possible to the required magnitude.
  • Such current sources may comprise a multi-stage amplifier, with the input signal being applied to an input of a first stage and the current output being provided by an output stage.
  • the output stage frequently consists of a single transistor, with the feedback signal being derived from the emitter circuit of the transistor.
  • a current source arrangement in which the magnitude of current flow in an output path of an amplifier stage is arranged to be dependent on the magnitude of an input signal applied to an amplification stage preceding said amplifier stage, there are provided also at least two feed back paths from said amplifier stage to said preceding amplification stage, one of which feed back paths serves to inject into the amplification stage a negative feed back signal whose magnitude is dependent on the current flow in said output path, another one of the feed back paths being arranged to transmit a signal dependent on a current flowing in an input to said amplifier stage such as to reduce the dependence of the current flow in said output path on the gain of said amplifier stage.
  • a current source arrangement in which the magnitude of current flowing in an output path of a transistor amplifier stage is arranged to be controlled by a control signal applied to an input of the arrangement, said control signal being applied to the transistor amplifier stage by way of a differential amplifier to an input of which is also applied a negative feedback signal whose magnitude is dependent upon that of said current in said output path, there are provided means to provide a further feedback signal to an input of said differential amplifier whose value is dependent upon the input current to said transistor amplifier stage such as to reduce the dependence of the current flowing in said output path on the gain of the transistor amplifier stage.
  • the control signal and the said further feedback signal are conveniently applied to a noninverting input of the differential amplifier, and the negative feedback signal to an inverting input thereof.
  • the negative feedback signal may be derived from the voltage drop across a resistive element in the emitter circuit of an output transistor in the transistor amplifier stage.
  • the said further feedback signal is conveniently derived from a first resistive element in the control signal input path of the transistor amplifier and applied to the non-inverting input via a second resistive element, with the control signal being applied to the same input of the differential amplifier via a third resistive element.
  • a current source arrangement comprises a differential amplifier having inverting and non-inverting inputs and an output, and a transistor having an input electrode, an output electrode, and a control electrode, the input electrode being connected by way of a resistive element to one pole of power supply means and the output electrode being connected by way of a load circuit to the other pole of said power supply means, the output of the differential amplifier being electrically coupled to the control electrode of the transistor, means to apply a control signal to one input of the differential amplifier, feedback means to apply to another input of the differential amplifier a signal dependent upon the voltage developed in operations across said resistive element, and further means for deriving a signal dependent on the current flow through the control electrode of the transistor, said further means being electrically connected to said one input of the differential amplifier.
  • said differential amplifier is a high gain amplifier having substantially linear amplification characteristics, of the kind known as operational amplifiers.
  • Said further means for deriving a signal dependent on the current flow through the control electrode of the transistor conveniently comprises a first resistive element connected between the output of the differential amplifier and the control electrode of the transistor, thereby also electrically coupling said output to said control electrode, a second resistive element by means of which the output of the differential amplifier is connected to said one input thereof, and a third resistive element connecting said one input thereof, and a third resistive element connecting said one input to a source of said control signal whereby said control signal is applied to said one input.
  • the control signal applied in operation of the current source to said one input may be a DC signal voltage derived from a resistance divider network.
  • Said control signal may also include an AC component superimposed on the DC signal in a known manner.
  • a current source arrangement in accordance with the present invention is suitable for use with electronic line units for telephone systems.
  • a current source arrangement in accordance with the present invention will now be described by way of example with reference to the accompanying drawing, of which:
  • Figure 1 shows the current source arrangement schematically
  • FIG. 2 shows the current source arrangement diagrammatically
  • FIG. 3 shows, in diagrammatic form, a circuit incorporating two complimentary current source arrangements in push-pull mode.
  • a current source in accordance with the present invention comprises a high gain linear amplification stage provided by an operational amplifier 1, and an amplifier stage in the form of a junction transistor 2, whose control electrode, or base, 8 is electrically coupled with the output of the amplifier 1.
  • the input electrode, or emitter 7 , of the transistor 2 is connected to the inverting input of the amplifier 1 and also, via a close tolerance resistor 8, to a voltage rail 9.
  • a voltage source 11 Connected to the non-inverting input of the amplifier 1 is a voltage source 11 supplying a control signal voltage to the amplifier and hence to the base 8 of the transistor 2, the value of the control voltage determining the current flow at the output electrode, or collector 6, of the transistor 2.
  • control means 4 and 5 are connected to the non-inverting input and the output respectively of the amplifier 1, arranvged to derive a signal dependent on base current of the transistor 2 and to apply a signal to the non-inverting input of the amplifier 1 such that the dependence of the collector current on the gain of the transistor is reduced.
  • a load circuit (not shown) to be driven by this current source arrangement is connected in use to the collector 6 of the transistor 2.
  • a signal indicative of the base current is derived by means 5 and is fed by means of the control means 4 into the non-inverting input of the amplifier, any deviation of this signal from its design value as determined by the control voltage causing a variation in the signal applied to the non-inverting input.
  • a consequent change in current flow through the emitter and hence the resistor 3 results in a ch ⁇ npre of the voltage applied to the emitter and thus compensates for this signal variation thereby bringing the collector current nearer to the intended value.
  • the output of the operational amplifier 1 is coupled by means of a resistor 16 to the base 8 of the transistor 2, whose emitter 7 is connected to the voltage rail 9 by way of a resistor 3 and to the inverting input of the amplifier 1 through a resistor 14 which serves as a feedback path and can also be arranged to equalize the source impedances to the two inputs of the amplifier.
  • a resistance divider network comprising resistors 18 and 19 connected across the voltage rails 9 and 10, from which power is also supplied to the amplifier 1, provides the biassing DC control voltage onto which may be superimposed an AC control voltage in the form of an AC signal applied to the terminal 20 of the capacitor 21.
  • biassing voltage derived from the resistance network 18, 19 and, where applicable, the AC signal is applied to the non-inverting input of the amplifier 1 through a resistor 17, with a resistor 15 connecting this input to the output of the amplifier.
  • the influence of resistors 14, 18, and 19 on the AC performance of the current source is negligible, the accuracy of the current source can be made dependent solely on resistor matching; thus obviating the need to adjust each individual source in dependence on the individual performance
  • V in the voltage obtained from the resistance divider network.
  • V ref the voltage at the non-inverting input of the amplifier.
  • V o the voltage at the output of the amplifier.
  • V b the voltage between base and emitter of the transistor
  • I b the base current of the transistor
  • I e the emitter current of the transistor
  • V o V ref (1 + k) + V bDc +I b R 16 (5)
  • Equation (17) shows thatvariations in g m are directly proportional to variations in R 3 , underlining the necessity for a very low tolerance resistor 3.
  • V bDc for a power transistor are + 100 mV resulting in a change of the collector current of approximately + 50 ⁇ A, i.e. + 0.2% of the quiescent current.
  • the near-independence of the output current with respect to the gain of the transistor as achieved in the fore-going current source arrangement allows easy matching of two or more such current source arrangements.
  • each of the two current sources making up the circuit comprises an operational amplifier 1, 1 , whose output is connected, by way of a resistor 16, 16 1 to the base of the transistor 2,2 1 respectively, with transistor 2 being an n-p-n transistor, and transistor 2 being a nominally matched, complementary p-n-p transistor.
  • the use of a matched pair of complementary transistors 2,2 1 provides for the impedance presented by each current source to the respective line of the two wire line 31 to be equal, since thereby the collectors 6 and 6 1 of the transistors 2 and 2 1 are connected respectively to the positive line (+) and the negative line (-) of the two wire line 31.
  • the other end of the two wire line 31 is connected to a load circuit (not shown) such as e.g. a subscriber's instrument.
  • each of the two current sources that is the negative feed back path via resistors 14 and 14 1 , and the further feed back path including resistors 15 and 16, and 15 1 and 16 1 respectively, are identical in arrangement and function to the corresponding feed back paths of the circuit shown in Figure 2.
  • the power supply to the arrangement is by means of voltage rail 29, carrying a negative voltage of suitable magnitude, and grounded voltage rail 30. lso connected between the voltage rails 29 and s a resistor divider network comprising resistors 22, 23, 24, 25, all having the same value, and equal resistors 19 and 19 1 .
  • This resistor network determines the average voltage of the two wire line, i.e. the mean of the voltages on the positive and the negative line of the two wire line 31.
  • the average voltage of the line pair lies half way between the voltage levels at rails 29 and 30. If, however, the two current sources are imperfectly matched, that is to say that they stabilize individually at different current levels of collector current for the same applied control input voltage, the average voltage of the two wire line 31 moves away from this half way point, in a direction so as to decrease the voltage between the collector and the corresponding current rail of that transistor which draws the higher current and increase the corresponding voltage at the other circuit.
  • This shift of the average voltage at the two wire line also termed common mode shift causes an equal and opposite change, with respect to the nearest current rail, of the input voltage levels Vm.
  • a differential voltage change on the other hand, which causes the two lines of the two wire line 31 to move individually away from the average voltage in opposite directions, leaves the average voltage unchanged, and thus will produce no change in the levels of V in and V in . If therefore an antiphase AC signal is applied to the terminals 20 and 20 1 , and the output currents I c and I c 1 vary, in antiphase, in accordance with that signal, no feed back effect will be produced.
  • the resistors 22 to 24 are approximately equal to twice the appropriate value of resistor 18 of Figure 2 in order to leave the above calculations unchanged, the third feed back path does not, therefore interfere with the AC operation of the arrangement.
  • the currents I c and I c 1 are not affected by any differential signal produced within the two wire line, such as may be produced in a subscriber's instrument.
  • the collector currents I c and I c 1 are largely unaffected by differential signals generated within the two wire line circuit, but respond only to either a common mode voltage shift, due to e.g. imperfect matching of the two current sources or an asymmetry in the line circuit on account of leakage currents, or to antiphase signals applied to the terminals 20 and 20 1 . Therefore, by providing a further circuit (not shown) which is unaffected by variations in the collector currents,
  • the present arrangement may be incorporated in, and form part of an electronic hybrid circuit.
  • the detection of such line generated signals may be achieved in the following way.
  • signals are sent to the subscriber's instrument, that is when antiphase signals are applied to the terminals 20 and 20 1 , then the emmiter and collector voltages generated by a given transistor are out of phase with each other, and by suitable addition these voltages may be made to cancel each other, and consequently no output signal is provided by said further circuit.
  • Differential signals which are generated within the line circuit do, however, produce in-phase collector and emmiter voltages at each of the transistors, resulting in an output signal at the said further circuit.
  • the arrangement including a said further circuit thus provides for a separation of incoming and outgoing signals as is required for an electronic hybrid circuit such as may be used in the conversion from two wire to four wire transmission and vice versa.
  • Resistors 26 and 27. and non-linear devices 28 and 29 on the positive and the negative line respectively form part of an overvoltage or lightning protection arrangement.
  • the devices 28 and 29 may e.g. be non-linear resistors, or zener diodes.
  • known means for providing the DC control voltages other than resistor divider networks may of course be employed, and any other modifications of the current sources above, which are obvious to those skilled in the art are included in the scope of the present invention.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Amplifiers (AREA)

Abstract

Une source de courant dont le courant de sortie d'un etage amplificateur de sortie (2) est commande par un signal d'entree, ayant son origine dans une source de signaux (11), allant vers un etage amplificateur d'entree (1) comprend, en plus d'un circuit de contre-reaction allant du circuit d'entree du courant de l'etage de sortie (2) a l'amplificateur d'entree (1), des moyens de controle (5) dans le circuit d'entree des signaux a l'amplificateur de sortie (2) et des moyens de commande (4) dans un circuit d'entree a l'amplificateur d'entree (1). Les moyens de controle (5) controlent les intemites des courants dans le circuit d'entree a l'amplificateur de sortie (2) et envoient, via les moyens de commande (4), un signal a l'amplificateur d'entree (1) de sorte que la dependance de l'intemite du courant dans le circuit de sortie du courant par rapport au gain de l'etage de sortie (2) est reduite. Un circuit est decrit, ainsi qu'une application a la transmission d'une ligne d'un abonne au telephone en utilisant deux sources de courant fonctionnant en push-pull.
PCT/GB1978/000041 1977-11-15 1978-11-14 Sources de courant WO1979000295A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE19782857168 DE2857168A1 (de) 1977-11-15 1978-11-14 Current sources

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB47475/77 1977-11-15
GB4747577A GB1602296A (en) 1977-11-15 1977-11-15 Current sources

Publications (1)

Publication Number Publication Date
WO1979000295A1 true WO1979000295A1 (fr) 1979-05-31

Family

ID=10445118

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1978/000041 WO1979000295A1 (fr) 1977-11-15 1978-11-14 Sources de courant

Country Status (6)

Country Link
BE (1) BE872025A (fr)
CA (1) CA1135349A (fr)
FR (1) FR2408948A1 (fr)
GB (1) GB1602296A (fr)
NL (1) NL7811241A (fr)
WO (1) WO1979000295A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0154366A1 (fr) * 1984-02-17 1985-09-11 Koninklijke Philips Electronics N.V. Circuit de transmission audio à amplificateur de transmission sous forme d'un stabilisateur de tension de ligne
EP0194723A1 (fr) * 1985-03-11 1986-09-17 Koninklijke Philips Electronics N.V. Amplificateur de transmission à tension de référence variable ayant la forme d'un stabilisateur de tension de ligne
GB2242289A (en) * 1990-02-07 1991-09-25 Mitsubishi Electric Corp Excitation current controller for automotive electromagnetic clutch

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2135846B (en) * 1983-02-04 1986-03-12 Standard Telephones Cables Ltd Current splitter

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2960660A (en) * 1957-06-07 1960-11-15 Lenkurt Electric Co Inc Feedback amplifier circuit
US3979688A (en) * 1974-05-15 1976-09-07 Analog Devices, Inc. Transistor amplifier of the Darlington type with internal bias providing low offset voltage and offset current drift
DE2626570A1 (de) * 1976-06-14 1977-12-22 Sachs Systemtechnik Gmbh Vorrichtung zur regelung und ueberwachung der stromversorgung eines wasserentkeimungsgeraetes

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2960660A (en) * 1957-06-07 1960-11-15 Lenkurt Electric Co Inc Feedback amplifier circuit
US3979688A (en) * 1974-05-15 1976-09-07 Analog Devices, Inc. Transistor amplifier of the Darlington type with internal bias providing low offset voltage and offset current drift
DE2626570A1 (de) * 1976-06-14 1977-12-22 Sachs Systemtechnik Gmbh Vorrichtung zur regelung und ueberwachung der stromversorgung eines wasserentkeimungsgeraetes

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
IBM Technical Disclosure Bulletin, Vol. 10, N° 7, published 7th December 1967 (Armonk, New York), R.E. May Jr:, "Current supply", page 1045 *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0154366A1 (fr) * 1984-02-17 1985-09-11 Koninklijke Philips Electronics N.V. Circuit de transmission audio à amplificateur de transmission sous forme d'un stabilisateur de tension de ligne
EP0194723A1 (fr) * 1985-03-11 1986-09-17 Koninklijke Philips Electronics N.V. Amplificateur de transmission à tension de référence variable ayant la forme d'un stabilisateur de tension de ligne
GB2242289A (en) * 1990-02-07 1991-09-25 Mitsubishi Electric Corp Excitation current controller for automotive electromagnetic clutch
US5179496A (en) * 1990-02-07 1993-01-12 Mitsubishi Denki K. K. Excitation current device for automotive electromagnetic clutch
GB2242289B (en) * 1990-02-07 1993-12-08 Mitsubishi Electric Corp Excitation current control device for automotive electromagnetic clutch

Also Published As

Publication number Publication date
FR2408948B1 (fr) 1984-05-04
FR2408948A1 (fr) 1979-06-08
NL7811241A (nl) 1979-05-17
CA1135349A (fr) 1982-11-09
GB1602296A (en) 1981-11-11
BE872025A (fr) 1979-03-01

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