US3753131A - Current source for supplying a current having an exponential wave form - Google Patents

Current source for supplying a current having an exponential wave form Download PDF

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Publication number
US3753131A
US3753131A US00214286A US3753131DA US3753131A US 3753131 A US3753131 A US 3753131A US 00214286 A US00214286 A US 00214286A US 3753131D A US3753131D A US 3753131DA US 3753131 A US3753131 A US 3753131A
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current
current source
reactance
input terminal
terminal
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US00214286A
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English (en)
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P Kramer
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US Philips Corp
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US Philips Corp
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    • 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
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06G—ANALOGUE COMPUTERS
    • G06G7/00—Devices in which the computing operation is performed by varying electric or magnetic quantities
    • G06G7/12—Arrangements for performing computing operations, e.g. operational amplifiers
    • G06G7/24—Arrangements for performing computing operations, e.g. operational amplifiers for evaluating logarithmic or exponential functions, e.g. hyperbolic functions

Definitions

  • Cited source may be used in analogue computers for opera- UNITED STATES PATENTS tions with logarithms, in apparatus for testing semicon- 3,696,304 10/1972 Fricke 330/1 A uc ors and in measuring instruments provided with a 3,477,034 11/1969 Gioia 330/69 logarithmic display. 3,237,002 2/1966 Patmore 330/40 3 Claims, 3 Drawing Figures CURRENT SOURCE FOR SUPPLYING A CURRENT HAVING AN EXPONENTIAL WAVE FORM
  • the invention relates to a current source for producing a current having an exponential. wave form, which circuit comprises a first and a second terminal for connection to a load, a reactance, resistors and a differential amplifier provided with a first and. a second, input terminal, an output terminal and a common lead.
  • Current sources are known. They generally are in the form of a two-terminal device between which a load may be connected so that the load passes a current which within certain limitsis independent of the value of the load.
  • the current source comprises a high-tension voltage supply having a large internal resistance, so that in the case of comparatively small loads the current is determined by the voltage and the high internal resistance.
  • a function generator may be used which produces the required function and delivers it output quantity, usually a voltage, to a final stage which is connected as a current source.
  • a current source for supplying a current having an exponential waveform of the type described at the beginning of the specification is characterized in that the output terminal is connected through a first resistor to the first input terminal and through the reactance to the second input terminal, the first load connection terminal being connected through a second resistor to the first input terminal and through a third resistor to the second input terminal, the common lead being connected to the second load connection terminal.
  • the differential amplifier may be of the operational amplifier type, providing large amplification and a high input impedance.
  • the current source circuit enables an exponential waveform extending over several decades to be obtained with a satisfactory degree of accuracy.
  • the initial condition may simply be set by imparting an initial charge to the capacitor via switches.
  • I Ac where I is the current of the circuit and e is the base of the natural logarithm
  • the constant A is determined by the said initial charge and by the values of the capacitor and the resistors
  • B is inversely proportional to a time constant fixed by these values.
  • the capacitor may be replaced by an inductor to which an initial current is supplied to fix the initial condition.
  • FIG. 1 is a circuit diagram of the current source according to the invention
  • FIG. 2 is a circuit diagram of a current source using a capacitor and a starting circuit
  • FIG. 3 is a circuit diagram of an embodiment using an inductor and an associated starting cirucit.
  • the current source shown has terminals 1 and 2 load B is to be connected.
  • a differential amplifier 3. having input terminals 4 and 5 and a common lead 6 is fed from supply sources, not shown.
  • An output terminal 7 supplies current which through a reactance Z and a resistor R and through the series combination of resistors R and R, is available to the load B at the terminal 1. The current returns via the terminal 2 and the lead 6.
  • the reactance Z is connected to the input terminal 4 and to the output terminal 7 of the amplifier, wilst the resistor R is connected between the input terminal 4 and the terminal 1.
  • the inputterminal 5 is connected to the junction point of the resistors R, and R,.
  • the switch 8 is coupled to a switch 9 capable of switching a capacitor 10.
  • the capacitor 10 In the rest position of the two switches, which position is shown in the Figure, the capacitor 10 is connected in parallel with the capacitor C. In the operative positions of the two switches, which are mechanically coupled to one another, the capacitor 10 is charged from a direct-voltage supply source connected to terminals 11 and 12.
  • the value of the capacitor i0 is very small compared with that of the capacitor C, so that when determining the time constant of the circuit the latter capacitor only need be taken into account and on the other hand when the switches 8 and 9 are in their rest positions the charge distribution between the two capacitors is such that when the circuit is started only a small voltage is set up across the capacitor C, for example a voltage of the order of microvolts or at most millivolts, whilst at the same time the directvoltage supply source voltage across the terminals 11 and 12 may be, say, 12 volts.
  • the reactance is a coil L having an inductance L.
  • the current satisfies the relationship: I: (R2 a z) e l 3 2 where i,,, is the initial current through the coil which is necessary when starting the circuit.
  • the time constant is given by:
  • a switch 8 By means of a switch 8 the coil is short-circuited and the circuit is brought to the starting condition in which the current I is zero. In this condition the current i,,, is produced in the magnetic circuit in the coil by a current in a separate winding 13 which is supplied via a switch 9 and a resistor 14 by a source connected to the terminals 1 l and 12. Since the switches 8 and 9 are mechanically coupled to one another, at the starting of the circuit the short-circuit of the coil L is removed and a current i,,, is produced in the coil L.
  • the current supply circuit according to the invention may be used to advantage in analogue computer circuits, an apparatus for testing semiconductors, where an e-power function is frequently met with, and in measuring instruments in which a logarithmic display of measurements is desired.
  • Current source for producing a current having an exponential waveform which circuit comprises a first and a second terminal for connection to a load, a reactance, resistors and a differential amplifier provided with a first and a second input terminal, an output terminal and a common lead, characterized in that the output terminal is connected through a first resistor to the first input terminal and through the reactance to the second input terminal, the first load connection terminal being connected through a second resistor to the first input terminal and through a third resistor to the second input terminal, whilst the common lead is connected to the second load connection terminal.
  • the reactance is a capacitor the capacitance value of which together with the first, second and third resistors determines the time constant of the exponential waveform and which by means of switches may be short-circuited to return the current source to the starting position and also may be provided with an initial charge by means of which, when the current is started, and by means of the values of the capacitor and the resistor the proportionality constant of the current may be fixed.
  • the reactance is an inductor the value of which together with the first, second and third 9 resistors determines the time constant of the exponential waveform and which by means of switches may be short-circuited to return the current source to the starting position and also may be provided with an initial current i so that, when the current is started, by this initial current and by the values of the inductor and the resistors the proportionality constant of the circuit current may be fixed.
  • current source as claimed in claim'il, character ized in that the reactance comprises a capacitor having a capacitance value which, together with the first, second and third resistors determines the time constant of the exponential waveform, and switching means by means of which the capacitor may be short-circuited to return the current source to a starting position and by which the capacitor also may be provided with an initial charge so that, when the current is started, and
  • Livy n'aeans of the values of the capacitor and the resistors the rtionality constant of the current may be fixed.
  • a current source for producing a current having an exponential waveform comprising, a first and a second terminal for connection to a load a reactance a luralit of resistors a differential amplifier provided with a first and a second input terminal, an output terminal and a common lead, means .1
  • the reactance comprises an inductor having an inductance value which, together with the first,
  • second and third resistors determines the time constant of the exponential waveform
  • switching means for short-circuiting the inductor to return the current source to a starting position and also for providing the inductor with an initial current i so that, when the current is started, the initial current and the values of the inductor and the resistors fix the proportionalityconstant of the current.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Software Systems (AREA)
  • Computer Hardware Design (AREA)
  • Electromagnetism (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Amplifiers (AREA)
  • Testing Electric Properties And Detecting Electric Faults (AREA)
US00214286A 1971-01-08 1971-12-30 Current source for supplying a current having an exponential wave form Expired - Lifetime US3753131A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL7100277A NL7100277A (enExample) 1971-01-08 1971-01-08

Publications (1)

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US3753131A true US3753131A (en) 1973-08-14

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US00214286A Expired - Lifetime US3753131A (en) 1971-01-08 1971-12-30 Current source for supplying a current having an exponential wave form

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US (1) US3753131A (enExample)
CA (1) CA958812A (enExample)
DE (1) DE2165180A1 (enExample)
FR (1) FR2121302A5 (enExample)
GB (1) GB1378792A (enExample)
IT (1) IT951075B (enExample)
NL (1) NL7100277A (enExample)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4721942A (en) * 1983-03-11 1988-01-26 Benedek Robin A Calibration warning apparatus

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE910427C (de) * 1941-03-12 1954-05-03 Siemens Ag Verstaerker mit zweifacher Rueckkopplung
US3113274A (en) * 1960-06-22 1963-12-03 Westinghouse Air Brake Co Analog squaring device
US3237002A (en) * 1962-06-28 1966-02-22 Electronic Associates Backlash simulator
US3436673A (en) * 1965-11-22 1969-04-01 Monsanto Co Converter circuit
US3477034A (en) * 1966-12-14 1969-11-04 Monsanto Co Zero suppression circuit for differential amplifiers
US3521082A (en) * 1967-08-15 1970-07-21 Honeywell Inc Linear/log time ramp generator
US3696304A (en) * 1970-06-29 1972-10-03 Monsanto Co Proportional only process controller

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE910427C (de) * 1941-03-12 1954-05-03 Siemens Ag Verstaerker mit zweifacher Rueckkopplung
US3113274A (en) * 1960-06-22 1963-12-03 Westinghouse Air Brake Co Analog squaring device
US3237002A (en) * 1962-06-28 1966-02-22 Electronic Associates Backlash simulator
US3436673A (en) * 1965-11-22 1969-04-01 Monsanto Co Converter circuit
US3477034A (en) * 1966-12-14 1969-11-04 Monsanto Co Zero suppression circuit for differential amplifiers
US3521082A (en) * 1967-08-15 1970-07-21 Honeywell Inc Linear/log time ramp generator
US3696304A (en) * 1970-06-29 1972-10-03 Monsanto Co Proportional only process controller

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Levin, Band Switching an Active Filter page 611, IBM Tech. Disclosure Bulletin Vol. 13, Aug. 1970. *
Philbrick/Nexus Research Applications Manual for OP Amps 1968, pages 53, 54, 66, 86, 96, 97, and 102. *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4721942A (en) * 1983-03-11 1988-01-26 Benedek Robin A Calibration warning apparatus

Also Published As

Publication number Publication date
IT951075B (it) 1973-06-30
GB1378792A (en) 1974-12-27
FR2121302A5 (enExample) 1972-08-18
NL7100277A (enExample) 1972-07-11
DE2165180A1 (de) 1972-07-27
CA958812A (en) 1974-12-03

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