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Constant Current Circuits
Last Updated on:
Friday, October 03, 2014 10:36 AM


Circuits Designed by Dave Johnson, P.E. :

  • 1 Amp Current Injector -  When you need to measure resistance down to a few micro ohms, this circuit works great. It is powered from two "C" cell batteries and is designed to inject a well regulated one amp of current into the unknown resistance. By measuring the voltage drop across the resistor with a digital voltmeter, the resistance value can be accurately measured. The circuit also is equipped with a low battery monitor. Published in Popular Electronics, November 1992


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

1 Amp Current Injector -  When you need to measure resistance down to a few micro ohms, this circuit works great. It is powered from two "C" cell batteries and is designed to inject a well regulated one amp of current....Published in Popular Electronics, November 1992 …. [Hobby Corner Circuit by Dave Johnson]
AN-D16: LND1 Series: Constant Current Sources And -  Supertex Semiconductors  (app note added 2/06)
AN-D18: DN25 Series: Constant Current Sources And -  Supertex Semiconductors  (app note added 2/06)
Bipolar current-source maintains high output impedance at high frequencies -  5-Dec-05 Issue of EDN  Use line-receiver/amp ICs to build high-frequency constant-current sources.... [Design Idea by Alex Birkett, University College London, Hospital National Health Service, London, UK]
Build a precise DC floating-current-source -  18-Aug-05 Issue of EDN  Use a general impedance converter and resistors to develop a specialized current source.... [Design Idea by By D Ramírez, S Casans, C Reig, AE Navarro, and J Sánchez, University of Valencia, Burjassot, Spain]
Circuit Forms Constant Current SCR -  02/01/01 EDN-Design Ideas:....[Design Idea added 11/05]  EDN is migrating links. This link is not verified.  Google the "title" + EDN for new link.
Circuit forms novel floating current-source -  1-May-03 Issue of EDN  Figure 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 in biomedical and environmental applications, for example. The circuit in Figure 1 is extremely simple; it sets fixed-bias conditions for ISFET sensors (VDS=I0 RX; IDS=I0].... [Design Idea by S Casans, AE Navarro, and D Ramirez, University of Valencia, Burjassot, Spain]
Circuit provides constant-current for ISFETs/MEMFETs -  26-Oct-00 Issue of EDN-Design Ideas  ISFETs and MEMFETs (ion-sensitive and membrane FETs] are solid-state chemical sensors that provide an electrical signal associated with the change of a….[Pdf contains several circuits, scroll to find this one…. [Design Idea by S Casans, D Ramirez, and AE Navarro, University of Valencia, Burjassot, Spain]
Circuit provides constant-current load for testing batteries -  19-Feb-09 Issue of EDN  A 9V battery provides power for a constant-current source for testing AA- or AAA-size batteries.... [Design Idea by Vladimir Rentyuk, Modul-98 Ltd, Zaporozhye, Ukraine]
Constant Current Amplifier -  (diagram added 6/03)
Constant Current Battery Charger -  A simple method of charging a battery from a higher voltage battery is shown in the circuit below to the left. Only one resistor is needed to set the desired charging current and is calculated by dividing the difference in battery voltages by the charge current. So, for example if 4 high capacity (4000 mA hour) ni-cads are to be charged at 300 mA from a 12 volt battery, the resistor need,.... [Bill Bowden's website]
Constant Current Charger -  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.... [John Nooyen's electronic schematic]
Constant current, constant voltage converter drives white LEDs -  2-Sep-04 Issue of EDN  LEDs usually take their drive from a constant dc-current source to maintain constant luminescence. Most dc/dc converters, however, deliver a constant voltage by comparing a feedback voltage to an internal reference via an internal error amplifier. The easiest way to turn a simple dc/dc converter into a constant-current source is to use a sense resistor to convert the output current to a voltage.... [Design Idea by Keith Szolusha, Linear Technology Corp, Milpitas, CA]
DAC and flip-flops form constant-current-source -  23-Apr-09 Issue of EDN  Using two flip flops, you can program a serial-input DAC to produce a constant 4 mA.... [Design Idea by Marián Štofka, Slovak University of Technology, Bratislava, Slovakia]
DN25 Series: Constant Current Sources -  Supertex Semiconductors  (app note added 2/06)
High Voltage Linear Regulator & Constant Current -  Supertex Semiconductors (app note added 6/06)
LND1 Series: Constant Current Sources -  Supertex Semiconductors  (app note added 2/06)
LT1511 Low Dropout Constant-Current/Constant-Voltage 3a Battery Charger -  DN144  Design Notes (Linear Technology) (app note added 6/06)
OpAmp can source or sink current -  03/02/06 EDN-Design Ideas  Bipolar current source beats familiar Howland-current pump....EDN is migrating links. This link is not verified.  Search the "title" + "EDN" for new link.
Shunt Constant Current Source -  This extremely simple circuit works well and may be just the thing in certain situations.  Output current is approximately 600mV divided by R2. [Designed by Andrew R. Morris]
Signal Sources Conditioners & Power Circuitry -  AN98 Linear Technology Eighteen circuits are presented in this compilation. Signal sources include a voltage controlled current source, an amplitude/frequency stabilized sine wave oscillator, a versatile, 0V to 50V wideband level shift and four sub-nanosecond pulse generators with risetimes as low as 20ps. Five signal conditioners appear; a unique,.... (added 9/06)
Simple dual constant-current load tests low-current power supplies -  21-Jun-07 Issue of EDN  You can use a simple 9V-battery-powered constant-current load to test small power supplies at various loads.... [Design Idea by John S Lo Giudice, STMicroelectronics, Schaumburg, IL]
Simple 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 solution.….must register on this site... [Published in Elecktor July/August 2010]
Simple 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.... (added 4/05)
TSM108 Evaluatin Board 12V to 6V DC/DC Converter -  The TSM108 is a step down controller that features constant voltage and constant current regulation.The Evaluation Board was designed to allow different converter configurations. Several options for power semiconductor footprints are available on the PCB in order to make it adaptable to a wide range of converter output power. In a first step,....  (app note added 3/05)
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.... (added 4/05)
Zener oscillators -  These two circuits are interesting from an academic point of view. Their practical implementation is rather critical and it is not easy to get steady operation. Circuit (a) requires a "cooked" zener: connect it first to a constant current generator, then increase the current.... (added 9/07)

 
 

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