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Current Source / Sink Circuits




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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 ….(designed by David A. Johnson)
1 Hz to 100 MHz VFC Features 160 DB Dynamic Range - 09/01/05 EDN-Design Ideas: Transform voltage to current over wide frequency, amplitude.....(design idea)
40 Volt Current Source Operates From  40 to +85°C - 06/22/95 EDN-Design Ideas: Wide-output-current-range sources that accommodate a wide supply and temperature range require special consideration.  basic circuit of ( Fig 1)provides IOUT = VREF/RS; typically, VREF is 1.25V for….....(design idea)
4–20ma Current Loop Tester - This circuit injects an adjustable current through a wire loop.  Using a digital current meter, the current can be adjusted from near zero to over 24 milliamps.  (designed by David A. Johnson)
60 MCurrent Source Feeds Telecomm Lines - 12/12/97 EDN-Design Ideas: (design idea)
6v NMH/NiCd 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. (designed by David A. Johnson)
A Simple Current-Sense Technique Eliminating a Sense Resistor AN-7 - Application Note 7 from Microsem  (app note)
Amplifier & Current Source Emulate Instrumentation Amplifier - 11/13/03 EDN-Design Ideas: The classic three or two-op-amp instrumentation-amplifier circuits are standard ways to amplify a small-amplitude differential signal contaminated with high common-mode noise. In some applications,  signal source is floating with high-series-output impedance and thus requires an appropriate high-input-impedance amplifier.....(design idea)
AN-1244: Photo-Diode Current-To-Voltage Converters - National Semiconductor Application Note  (app note)
AN-240: Wide-Range Current-To-Frequency Converters - National Semiconductor Application Note  (app note)
AN-D16: Lnd1 Series: Constant Current Sources And - Supertex Semiconductors  (app note)
AN-D18: Dn25 Series: Constant Current Sources And - Supertex Semiconductors  (app note)
Basic Current Source  - Circuit Ideas for Designers Application Notes Advanced Linear Devices, Inc.  (app note)
Bipolar current source maintains high output impedance at high frequencies - 12/05/05 EDN-Design Ideas: Use line-receiver/amp ICs to build high-frequency constant-current sources.....(design idea)
Bipolars Provide Stable Current Source - 09/24/98 EDN-Design Ideas: (design idea)
Buffered Current Source - Circuit Ideas for Designers Application Notes Advanced Linear Devices, Inc.  (app note)
Build a Precise DC Floating Current Source - 08/18/05 EDN-Design Ideas: Use a general impedance converter and resistors to develop a specialized current source.....(design idea)
Cascode Current Source  - Circuit Ideas for Designers Application Notes Advanced Linear Devices, Inc.  (app note)
Circuit Forms Novel Floating Current Source - 05/01/03 EDN-Design Ideas: 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)
Circuit provides constant current for ISFETs/MEMFETs - 10/26/00 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....(design idea)
CMOS Buffer Delivers Precise Current Pulses - 12/08/94 EDN-Design Ideas: The circuit in Fig 1 delivers stable, fast-settling reference-current pulses. You can use the circuit in systems employing A/D, D/A, or V/F converters. Digital input pulses, VP, connect to IC3B, a 74AC240 buffer. The 5.00V reference, IC1, constrains IC3B's output, VR, to either VREF or0V. IC3B's rise and fall times are <3 nsec.....(design idea)
Computer Controlled 100ma Current Source - Often in industrial control systems a constant current source is needed, which is controlled by a computer and referenced to circuit ground. The circuit below converts a zero to 5v signal from a computer’s analog output into a current, with a full scale of 100ma. The circuit shown requires a 9v DC supply but any voltage from 9v to 12v will work. ….(designed by David A. Johnson)
Constant Current Amplifier  - (electronic diagram)
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,....(circuit)
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 / circuit)
Constant Current Constant Voltage Converter Drives White LEDs - 09/02/04 EDN-Design Ideas: 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.....(design idea)
Constant Current LED Driver - Bob Pease from National Semiconductor came up with this circuit and I have used it many times.  It maintains a constant current through one or more LEDs.  A single resistor controls the desired current. (designed by David A. Johnson)
Current Regulators - I have been asked a couple times about constant current regulators. Here are a couple simple ones. Set R2 on both circuits for 0.6 volts at the desired current. Select Q1 and select R1 according to the amount of current you would like to source or limit. (circuit)
Current Source - Getting optimum performance in certain applications requires that some components, sensors, DC motors, transistors, be driven or biased by a constant current. We're mostly familiar with voltage regulators and their ability to maintain a constant voltage under varying current conditions. In this application, your challenge is to provide a constant ...(spice design)
Current Source & Sink Circuits Have Low Tc - 07/04/96 EDN-Design Ideas: (design idea)
Current Source Allows Measuring Three Wire Rtd - 07/06/00 EDN-Design Ideas: (design idea)
Current Source Enables OpAmp's Output to Go to Ground - 09/05/04 EDN-Design Ideas: The LM324 is a cost-effective choice for an op amp, especially when you need to apply ground-level inputs. Although its output purportedly includes ground, its poor current-sinking capability limits the applications. At output voltages lower than 0.5V, the op amp's sinking current ranges only from 2 to 100 µA.....(design idea)
Current Source Forms Unusually Simple Regulator - 09/12/97 EDN-Design Ideas:   -Simple regulator uses a switching current source to drive a pair of shunt Zener regulators, circuit produces ±15V dual outputs, for total output power of approximately400 mW form100-400-Volt DC source.....(design idea)
Current source has high compliance - 09/01/00 EDN-Design Ideas:.....(design idea)
Current Source has High Output Impedance - 06/22/00 EDN-Design Ideas:.....(design idea)
Current Source is Nonvolatile - 05/07/02 EDN-Design Ideas: Digitally programmable current sources that feature automatic trimming and retain the setting despite power-down cycles are useful in applications such as RFand laser-communications drivers. The circuit in Figure 1, for example, is particularly suited for setting the drive current for the optical pump in widely tunable VCSELs (vertical-cavity.....(design idea)
Current source makes novel Class a buffer - 04/03/08 EDN-Design Ideas: A pair of classic current sources in totem-pole configuration enables a novel Class A buffer.....(design idea)
Current Source Mirror - Circuit Ideas for Designers Application Notes Advanced Linear Devices, Inc.  (app note)
Current Source Multiplication - Circuit Ideas for Designers Application Notes Advanced Linear Devices, Inc.  (app note)
Current Source with Gate Control - Circuit Ideas for Designers Application Notes Advanced Linear Devices, Inc.  (app note)


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