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
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
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 David A. 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
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 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 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
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. Design by Dudley Nye
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
Test UL Ground Resistance - UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms. This resistance must be tested with actual line current in excess or 10 amps. The circuit shown uses a couple of LEDs to indicate. . . Circuit by David Johnson P.E.-April, 2001
Tests UL Ground Resistance - UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms. This resistance must be tested with actual line current in excess or 10 amps. The circuit shown uses a couple of LEDs to indicate if in fact the resistance is less than 0.1ohmsmodified on july 10, 2006 . . . Hobby Circuit designed by Dave Johnson P.E.-April, 2001
Thermally Controlled NiCad Charger - A voltage controlled current (maximum of 1A) is used to charge a NiCd battery. The control voltage is derived from the temperature difference between the battery and the ambient air. The charge current is reduced as the battery heats up. __ Linear Technology/Analog Devices App Note, Jun 21, 2011
Two Terminal 1A Current Source - The LT3080 linear regulator can easily be configured as a two terminal current source __ Linear Technology/Analog Devices App Note, Mar 24th 2010
Two Terminal 3A Current Source - The LT3083 is a 3A low dropout linear regulator that can be paralleled to increase output current or spread heat on surface mounted boards. Architected as a precision current source and voltage follower, this new regulator finds use in many applications requiring high current, adjustability to zero, and no heat sink. The device __ Linear Technology/Analog Devices App Note, Mar 9th 2011
Two Terminal 500mA Current Source - The LT3085 linear regulator can easily be configured as a two terminal current source __ Linear Technology/Analog Devices App Note, Mar 24th 2010
Two Terminal Current Regulator (LT1635) - The LT1635 combines an op amp with a 200mV reference. Scaling this reference voltage to a potential across resistor R3 forces a controlled amount of current to flow from the +terminal to the –terminal. Power is taken from the loop. __ Linear Technology/Analog Devices App Note, Mar 31, 2010
Two Terminal Current Source - The opamp buffers the upper potential of a shunt regulator to set a voltage drop on R1 equal to the reference. The net current to RL is the programmed R1 current plus the quiescent supply current of the opamp passing through the reference. __ Linear Technology/Analog Devices App Note, Jun 21, 2011
UL Ground Resistance Tester - UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0.1ohms. This resistance must be tested with actual line current in excess or 10 amps. The circuit shown uses a couple of LEDs to indicate. . . Circuit by David Johnson P.E.-April, 2001
Voltage Controlled Current Source - Adding a current sense amplifier in the feedback loop of an adjustable low dropout voltage regulator creates a simple voltage controlled current source. The range of output current sourced by the circuit is set only by the current capability of the voltage regulator. The current sense amplifier senses the output current and __ Linear Technology/Analog Devices App Note, Mar 31, 2010
Voltage Controlled Current Source with Ground Referred Input & Output - A flying capacitor device such as the LTC1043 can produce a precision voltage differential over a wide common mode range. Here it converts a ground referred input voltage directly to a differential voltage across a fixed resistor which then forces a precise current sourced at the circuit output. __ Linear Technology/Analog Devices App Note, Jun 21, 2011
Voltage-To-Current Conversion Amplifier - How to transform the passive voltage-to-current converter into an active one
Voltage-to-current converter drives white LEDs - 06/27/02 EDN-Design Ideas Reset generator uses "fleapower" = You sometimes need to drive a white LED from one 1.5V battery. Unfortunately, the forward voltage of a white LED is 3 to 4V. So, you would need a DC/DC converter to drive the LED from one battery. Using the simple circuit in Figure 1, you can drive one white LED or two series-connected green LEDs, using only a few components Design by Susanne Nell, Breitenfurt, Austria
Voltage-To-Current Converter Makes a Flexible Current Reference - 18-Sep-03 EDN-Design Ideas The voltage-to-current converter in Figure 1 can both source and sink current. The circuit isflexible than some traditional current references that require different topologies for current sourcing and sinking. Also, you can easily adjust the value of the current reference by simply adjusting the circuit's input voltage Design by Art Kay, Texas Instruments, Tucson, AZ
Voltage-to-Current converter offers precisely Defined Dead-band - 07/29/13 EDN-Design Ideas Dead-bands have application in control loops and other areas. In the control of nonlinear and linear systems, sometimes a slight nonlinearity is intentionally inserted into the closed control loop. “Slight” here means that the output of the inserted element starts to vary linearly, but only once the input exceeds a nonzero threshold value. For inputs from zero to the threshold, the output of the element has zero value. The result is that adding of this nonlinear element can quench damped oscillations, which are typical for feedback systems. Design by Marian Stofka |