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Current Source / Current Sink Circuits

Current Source Circuits:  #'s - B       C - G       H - S      T - Z
 

Last Updated: October 13, 2017 03:06 AM

Circuits Designed by Dave Johnson, P.E.

LED Driver using Constant CurrentLEDs are current driven devices.  The light they produce is proportional to the current flowing though them.  One way to maintain a fairly steady light output is to keep the current through the LED fixed, even as the supply voltage may change.  A classic. . . Circuit by Dave Johnson P.E.-December, 2010

NMH/NiCd 6v Battery TesterI designed this circuit to test rechargeable six volt battery packs under constant current conditions.  As designed, the circuit applies a 10 amp load to the battery pack.  A heat sink must be used on the main power transistor . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2004

One Amp Current InjectorI designed and built this thing many years ago.  I published the hobby circuit in the now defunct Radio Elecronics magazine back in 1992.  The electronic circuit injects a precise 1 amp of current into any unknown resistor, up to about two ohms.  Two alkaline . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

High Accuracy 10mA Current Source -  An external reference improves the initial accuracy and temperature drift of the LT3092 current source.  __ Linear Technology/Analog Devices App Note, Mar 24th 2010

High Output Impedance Current Mirror -  Circuit Ideas for Designers App Note___ Advanced Linear Devices, Inc

High Output Impedance Current Source -  Circuit Ideas for Designers App Note___ Advanced Linear Devices, Inc

High Voltage 100mA Current Source -  An external zener diodes protects the LT3092 and allows the part to be used in high voltage applications.  __ Linear Technology/Analog Devices App Note, Mar 24th 2010

High-speed regulator makes great current source -  07/16/98 EDN-Design Ideas (File has several circuits, please scroll to find this one)  To power a load that requires a high-compliance current source(for example, a plasma tube, such as an ion laser), a circuit must provide very accurate current control with a wide bandwidth and a voltage compliance of several hundred volts.  You can use a high-speed linear-regulatorFile has several circuits, please scroll to find this one__ Circuit Design by   Craig Varga, Linear Technology Corp, Milpitas, CA

IC Current Sources-LT3092 -  Current sources have been a well known but theoretical circuit component.  Unlike voltage sources, a 0.01% accurate 2-terminal current source has been an elusive component that is not easily available and difficult to design.  With the introduction of the LT3092, the current source as a drop-in component becomes a reality.  The __ Linear Technology/Analog Devices App Note, Robert Dobkin-Vice President-Engineering and Chief Technical Officer Sep 15th 2009

JFET cascode boosts current-source performance -  05/11/06 EDN-Design Ideas A constant-current source minimizes the reference circuit's sensitivity to supply-voltage fluctuations and extends the voltage reference's operating voltage beyond its 5.5V maximum rating__ Circuit Design by Clayton B Grantham, Tucson, AZ

Keep Current Drain Constant -  04/12/01  EDN-Design Ideas It is sometimes advantageous to keep the overall current consumption of an electronic device constant.  A large, seven-segment display, for example, draws nearly zero current when no segment is on to hundreds of milliamps when fully lit.  __ Circuit Design by Peter Guettler,APS Software Engineering GmbH, Cologne, Germany

LED Driver using Constant Current -  LEDs are current driven devices.  The light they produce is proportional to the current flowing though them.  One way to maintain a fairly steady light output is to keep the current through the LED fixed, even as the supply voltage may change.  A classic. . . Circuit by Dave Johnson P.E.-December, 2010

Linear Constant Current LED Lamp Dimmer -  This circuits drives 24 white light LEDs with an adjustable constant current __  

Low-Overhead Current Source -  This circuit has a very low overhead of just 120uA, and most of that is transistor base drive.  The voltage reference only uses 20uA of current.  Also, the circuit is designed to saturate if required, to maintain output current.  The overhead current quickly __ Designed by Andrew R. Morris

NMH/NiCd 6v Battery Tester -  I designed this circuit to test rechargeable six volt battery packs under constant current conditions.  As designed, the circuit applies a 10 amp load to the battery pack.  A heat sink must be used on the main power transistor . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2004

Novel Floating Current Source -  05/01/03  EDN-Design Ideas One-shot provIdeas frequency discriminationFigure 1 shows a polarization circuit applicable to ISFET (ion-sensitive field-effect-transistor] sensors.  ISFETs are solid-state chemical sensors that measure the pH value of a solution i__ Circuit Design by S Casans, AE Navarro, and D Ramirez, University of Valencia, Burjassot, Spain

One Amp Current Injector -  I designed and built this thing many years ago.  I published the hobby circuit in the now defunct Radio Elecronics magazine back in 1992.  The electronic circuit injects a precise 1 amp of current into any unknown resistor, up to about two ohms.  Two alkaline . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Parallel Current Sources for Higher Current 300mA Output -  The LT3092 can easily be paralleled for higher current outputs __ Linear Technology/Analog Devices App Note, Mar 24th 2010

PC Controlled Voltage or Current Source -  If you are interested in model aeroplanes and have the capital, a radio controlled electric park flyer is a must have.  An RC aeroplane under 400 grams floats around like the rubber models of my youth and contact with the ground doesn't seems to involve that sickening crunch __ Contact: r dot p @ webone.com.au

Peaking Current Source Has High Rejection -  EDN-Design Ideas -- 02/15/96    A cascade peaking current source significantly improves the output-current regulation compared to conventional and Widlar current sources but imposes only a minor increase in circuit complexity.  Peaking current sources are those with a characteristic operating point for which the output current is independent of the input current.  Consider the circuit in Figure 1a.__ Circuit Design by Michael Wyatt, Honeywell Inc

Precision Current Sink Costs Less Than $20 -  03/13/98 EDN-Design Ideas   NOTE :  File contains many circuits, please scroll to find this one.  Simple active load circuit for current from1 mA to1A and voltage from3 to40-Volt__ Circuit Design by Carlos Barberis, Bartek Technologies, Haverhill, MA

Precision Current Source -  A non-inverting amplifier configuration can force an input control voltage across a ground referred resistor.  This creates a precise amount of current flow.  This current must be sunk by the external transitors so the same amount of current flows from ground and sourced to a negative supply referred load circuit.  __ Linear Technology/Analog Devices App Note, Jun 21, 2011

Precision current source is software-programmable -  12/17/04  EDN-Design Ideas With the addition of a few inexpensive miniature components, the hard-wired, voltage-controlled current source of yesterday becomes a software-programmable voltage-controlled current source(Figure 1).  A digital potentiometer, IC1 in conjunction with a precision op amp, IC2, sets current through a pass transistor, ISET, and a shunt regulator, IC3, provIdeas a constant reference voltage across__ Circuit Design by Joe Neubauer, Maxim Integrated Products Inc, Sunnyvale, CA

Precision Ground Referenced Voltage Controlled Current Source -  The control voltage, Vin, is converted to a charge on a capacitor that is referenced to ground.  This charge is transferred to place a differential voltage across the output current programming resistor.  The output current then flows into a ground referenced load for a precision single supply circuit without the need for a voltage __ Linear Technology/Analog Devices App Note, Mar 16th 2010

Precision Nanoamp Bidirectional Current Source -  This circuit sources and sinks just nanoamps of current with precision due to the low input bias current of the CMOS op amps.  A buffered difference amplifier and an integrator force the voltage across a 10Megaohm set resistor to be 1/1000 of the control input voltage in either polarity.  __ Linear Technology/Analog Devices App Note, Mar 16th 2010

Precision programmable current source uses two ICs -  EDN-Design Ideas 11/20/2015    Here are some programmable current source Design Ideaswhich make good use of precision on-chip component matching__ Circuit Design by Stefano Salvatori & Pietro Oliva

Precision Voltage Controlled Current Source -  The ultra-precise LTC2053 instrumentation amplifier is configured to servo the voltage drop on sense resistor R to match the command VC.  The LTC2053 output capability limits this basic configuration to low current applications.  __ Linear Technology/Analog Devices App Note, Mar 31, 2010

Programmable Switching 1.5A Current Source -  The LTC3600 is a high efficiency, monolithic synchronous buck regulator whose output is programmed with just one external resistor.  The accurate internally generated 50μA current source on the ISET pin allows the use of a single external resistor to program an output voltage that ranges from 0V to 0.5V below VIN.  The VOUT __ Linear Technology/Analog Devices App Note, Jan 16th 2012

Reduced Power Infra-Red Diode Driver -  Infra-Red LEDs can be used as continuously operating beams of light.  Sensing a break in the path of light between the source and a photodiode receiver is often used in safety and alarm systems.  To extend the run-time of the light source, the diode conducts the minimum current necessary, in this case 10mA.  Controlling the duty __ Linear Technology/Analog Devices App Note, Mar 16th 2010

Reference stabilizes exponential current -  10/25/01 EDN-Design Ideas In an antilog converter, the difference between the base voltages of two transistors sets the ratio of their collector currents  The use of matched transistors balances the first-order temperature coefficient but leaves a temperature-dependent gain term, q/kT.  Classic antilog circuits use a thermistor in the drive circuitry to correct this temperature dependency__ Circuit Design by Tom Napier, North Wales, PA

Regulator Can Source & Sink Current -  12/07/95  EDN-Design Ideas Although a positive supply regulator usually acts solely as a current source, some applications require both sourcing and sinking.  For these applications, Linear Technology’s LT1118 family of low-dropout regulators can source and sink as much as 800 and 4__ Circuit Design by Bill Schweber Linear Technology Corp, Milpitas, CA.

Scheme keeps Current Drain Constant -  04/12/01  EDN-Design Ideas It is sometimes advantageous to keep the overall current consumption of an electronic device constant.  A large, seven-segment display, for example, draws nearly zero current when no segment is on to hundreds of milliamps when fully lit.  __ Circuit Design by Peter Guttler

Serves as milliohmmeter -  04/15/04 EDN-Design Ideas When I was recently debugging a design, I discovered that a short circuit existed from a ground plane to a power plane.  I did not have access to a milliohm meter or an equivalent tester for locating this type of short circuit.  So, I logged onto the Internet to find an easily constructible milliohm meter__ Circuit Design by AM Hunt, Lancaster Hunt Systems Ltd, Shepperton, UK

Simple Circuit Current-Source & Sink-Circuits Have Low T -  07/04/96 EDN-Design Ideas Most current-source and -sink circuits are either simple, precise, or low dropout.  The circuits in Figure 1 have the advantage of all three features and are also switchable.  Figure 1a was originally intended for the current-source side of an H-bridge drive for spacecraft torque rods.  Thus, high-reliability and radiation-tolerant components are not necessary.   __ Circuit Design by Carl R Anderson, Ball Aerospace, Boulder, CO

Simple Circuit Dual Constant-Current Load Tests Low-Current Power Supplies -  06/21/07  EDN-Design Ideas You can use a simple 9V-battery-powered constant-current load to test small power supplies at various loads__ Circuit Design by John S Lo Giudice, STMicroelectronics, Schaumburg, IL

Simple Circuit LED Constant Current Source -  Chip manufacturers are always coming up with ever more sophisticated constant current driver chips for LEDs.  We have included this design for those of you who prefer a more cheap and cheerful solutionmust register on this site __ Designed by Published in Elecktor July/Augu, 2010

Simple Circuit serves as milliohmmeter -  04/15/04 EDN-Design Ideas When I was recently debugging a design, I discovered that a short circuit existed from a ground plane to a power plane.  I did not have access to a milliohm meter or an equivalent tester for locating this type of short circuit.  So, I logged onto the Internet to find an easily constructible milliohm meter__ Circuit Design by AM Hunt, Lancaster Hunt Systems Ltd, Shepperton, UK

Simple Circuit Variable Voltage Source -  The high current regulator below uses an additional winding or a separate transformer to supply power for the LM317 regulator so that the pass transistors can operate closer to saturation and improve efficiency.  For good efficiency the voltage at the collectors of the two parallel 2N3055 pass transistors should be close to the output voltage.  The LM317 requires a couple extra volts on the input side, plus the emitter/base drop of the 3055s, plus whatever is lost across the (0.1ohm) equalizing resistors (1volt at 10 amps) , so a separate transformer and rectifier/filter circuit is used that is a few volts higher than the output voltage __ Designed by Bill Bowden

Simple Constant Current Source -  This simple constant current source uses an LM317 regulator IC.  N.  B.  The pin-outs of the IC are not a mistake, the output is taken from the adjustment pin.  I found this circuit to charge all my NiCad batteries, and I use a Kambrook mechanical light-timer (or equiv.) for 110vac to time the charge __ Designed by John Nooyen

Simplify Classic V/I Converter -  01/20/00 EDN-Design Ideas Figure 1 shows a classic voltage-to-current (V/I) converter.  You can select the resistor values such that the output current in the load, R L , varies only with the input voltage, V IN , and is independent of R L .  The circuit is widely used in industrial instruments for supplying a 4- to 20-mA signal.  __ Circuit Design by Dudley Nye

Single Supply Current Source for Platinum RTD -  The LT1800's Precision and low bias input stage is used to good advantage in Fig.5 Single Supply Current Source for Platinum RTD circuit.  R4 and C1 stabilize the circuit making it insensitive to cable characteristics.  Output is 1.00V at 0ºC and its gain factor is 3.85mV/ºC.  __ Linear Technology/Analog Devices App Notes, Jul 2nd 2012

Step Up/Step Down Converter Takes 2 to 16V Inputs -  07/16/98 EDN-Design Ideas (Several circuits in this file.  Scroll to find this one)  The circuit in Figure 1 is a low-cost step-up/step-down dc/dc converter.  By definition, its input can range above and below the regulated voltage.  The circuit includes a simple switchmode boost converter (IC1) that contains a comparator normally used to detect low battery voltage.   __ Circuit Design by Lucian Brodogna and  Luca Vasalli/ Maximin Integrated Products, Milan Italy

Step up/step-down current-source charges batteries -  06/06/96  EDN-Design Ideas For battery charging, the highly efficient step-down (buck] configuration is usually the topology of choice.  However, a different approach is necessary if the following conditions prevailThe supply voltage is less than the battery __ Circuit Design by Michael Keagy, Maxim Integrated Products, Sunnyvale, CA

Switching (PWM) Solenoid Driver -  This is a very simple circuit to interface a current loop sensor to an input which is designed for a voltage, such as that from a standard potentiometer.  This page is technical so that interested persons can build the circuit themselves, but 4QD can also supply the interface on a 'postage stamp' sized (22mm x 27mm) board as shown in the first diagram.  It is a relatively trivial circuit!  __ Designed by Richard Torrens

Switching regulator forms constant-current source -  05/30/02 EDN-Design Ideas Many applications require current sources rather than voltage sources.  When you need a high-current source, using a linear regulator is inadvisable, because of the high power dissipation in the series resistor.  To solve the wasted-power problem, you can use a switch-mode regulator.  The circuit of Figure 1 uses IC1, an LM2576 adjustable regulator__ Circuit Design by Stefan Strozecki, Institute of Telecommunications, bydgoszcz, Poland

Switchmode Constant Current Source -  Operating a stepper motor using a fixed (constant) voltage supply results in poor torque at high speeds.  In fact, stepper motors tend to stall at fairly low speeds under such conditions.  Several approaches can be used to overcome this problem, one of which is to use a constant current supply in place of the more __


Current Source Circuits:  #'s - B       C - G       H - S      T - Z

 


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