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Converters - Voltage to Current
Last Updated on: Thursday, April 07, 2016 01:01 PM

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Circuits Designed by Dave Johnson, P.E. :
  • 1 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 C cells power the complete circuit.  . . . [Circuit by David Johnson P.E.,  07/11/06]

  • 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 . . . [Circuit by David Johnson P.E.,  07/09/08]

  • 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 . . . [Circuit by Dave Johnson P.E.,  12/12/04]

  • 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 . . . [Circuit by David A. Johnson P.E.,  07/09/08] 

  • Constant Current Drives LEDs -  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 . . . [Hobby Circuit designed by David A. Johnson P.E.,  12/13/10] 

  • 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.  . . . [Hobby Circuit designed by David A. Johnson P.E.,  11/25/04] 

  • 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 - modified on July 11, 2006  . . . [Circuit by David Johnson P.E.,  06/04/00]

  • Current Source is Computer Controlled -  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 . . . [Hobby Circuit designed by Dave Johnson P.E.,  07/08/08]

  • Ground Resistance Tester -  UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0. 1 ohms.   This resistance must be tested with actual line current in excess or 10 Amps.   The circuit shown uses a couple of LEDs to indicat . . . [Hobby Circuit designed by Dave Johnson P.E.,  04/28/01]

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

±5A, 2.5V (2-Quadrant) μModule Voltage Regulator -  The LTM8052 is a 36VIN, 5A, 2-quadrant constant-voltage, constant-current (CVCC) step-down μModule® regulator. Included in the package are the switching controller, power switches, inductor and support components. Operating over an input voltage range of 6V to 36V, the LTM8052 supports an output voltage range of 1. 2V to 24V. . . .  [Linear Technology App Note - , Mar 30th 2012]

 

0A to 2A Current Source -  The LT1995 Amplifies the sense resistor drop by 5V/V and subtracts that from VIN, providing an error signal to an LT1880 integrator. The integrated error drives the PMOSFET as required to deliver the commanded current. . . .  [Linear Technology App Note - , ]

 

1 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 C cells power the complete circuit.  . . . [Circuit by David Johnson P.E.,  07/11/06]

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 . . . [Circuit by David Johnson P.E.,  07/09/08]

1-Hz to 100-MHz VFC features 160-dB dynamic range -  09/01/05  EDN Design Idea   Transform voltage to current over wide frequency, Amplitude. The VFC (voltage-to-frequency-converter) circuit in Figure 1 achieves a wider dynamic range and a higher full-scale output frequency—100 MHz with 10% overrange to 110 MHz—by a factor of 10 over any commercially available converter. The circuit's 160-dB dynamic range spans eight decades for a 0 to 5V input range and allows continuous operation down to 1 Hz. Additional specifications include 0. 1% linearity, a 250-ppm/°C gain/temperature coefficient, a 1-Hz/°C zero-point shift, and a 0. 1% frequency shift for a 10% power-supply- voltage variation. A single 5V supply powers the circuit. . . .  [by Jim Williams, EDN's most revered contributor-At 63 years of age, Williams passed away in June 2011 after a stroke.]

 

2-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 App Note - , Mar 9th 2011]

 

2-Terminal Temperature-to-Current Thermometer Suitable for Use at the End of Long Wire Runs -  By adding the LT3092 to a thermistor kit along with three 0. 1% accuracy resistors and one final trim, a very accurate 2-terminal temperature-to-current converter can be built. This circuit measures 700μA operating current at 0°C, dropping by 2μA every degree until 100°C, at which point the current measures 500μA. The obvious . . .  [Linear Technology App Note - , Oct 26th 2010]

 

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 . . . [Circuit by Dave Johnson P.E.,  12/12/04]

 

Adjustable Two Terminal 200mA Current Source -  The LT3092 requires only two resistors to set the current between 0. 5mA and 200mA . . .  [Linear Technology App Note - , Mar 24th 2010]

 

AN-1244: Photo-Diode Current-To-Voltage Converters -  Application Note. . .  [National Semiconductor]

 

Bidirectional Current Source -  The LT1990 is a differential Amplifier with integrated precision resistors. The circuit shown is the classic Howland current source, implemented by simply adding a sense resistor. . . .  [Linear Technology App Note - , Mar 31, 2010]

 

Bipolar current source maintains high output impedance at high frequencies -  12/05/05  EDN Design Idea   Use line-receiver/amp ICs to build high-frequency constant-current sources. . .  [by Alex Birkett, University College London, Hospital National Health Service, London, UK]

 

Build a Direct Current Converter -  To have a Direct Current Converter on your work bench increases greatly your capability of experimenting within an Ample range of electronic components that need over 100 volts to be driven. Among these components we find neon lamps, nixie display numerical tubes, and some kind of triode and pentode valves. Neon lamps open a broad field to build audio oscillators, blinkers and flashers, polarity finders, display decorations, hot chassis checkers. . .  [braincambre500 AT yahoo.com]

 

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 . . . [Circuit by David A. Johnson P.E.,  07/09/08]

 

Constant Current Drives LEDs -  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 . . . [Hobby Circuit designed by David A. Johnson P.E.,  12/13/10]

 

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.  . . . [Hobby Circuit designed by David A. Johnson P.E.,  11/25/04]

 

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 - modified on July 11, 2006  . . . [Circuit by David Johnson P.E.,  06/04/00]

 

Current Source is Computer Controlled -  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 . . . [Hobby Circuit designed by Dave Johnson P.E.,  07/08/08]

 

DAC Controlled 100mA Current Source -  The LT3092 easily interfaces with an external DAC to allow digital current control. . . .  [Linear Technology App Note - , Mar 24th 2010]

 

Design Formulas Simplify Classic V/I Converter -  01/20/00 EDN Design Idea   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, RL, varies only with the input voltage, VIN, and is independent of RL. The circuit is widely used in industrial instruments for supplying a 4- to 20-mA signal. The circuit has its limitations, however, because the resistor values must be quite accurate to obtain a true current source. The literature describing the circuit provides design methods that are for special cases or are for approximate designs. . . .  [by Dudley Nye

 

Gain-selectable IC yields voltage-to-current converter -  06/01/15  EDN Design Idea   A voltage-to-current converter Design Idea with no discrete components and excellent specs. . . .  [EDN Design Idea]

 

Ground Referred Precision Current Sources -  The zero drift LTC2054 instrumentation Amplifier can be used in conjunction with one of Linear Technology's precision, low temperature drift shunt voltage references (in this example the LT1634) to create a precision, ground referred current source. . . .  [Linear Technology App Note - , Mar 30th 2010]

 

Ground Resistance Tester -  UL requires that an electrical system using a metal chassis earth ground connection have a resistance of less than 0. 1 ohms.   This resistance must be tested with actual line current in excess or 10 Amps.   The circuit shown uses a couple of LEDs to indicat . . . [Hobby Circuit designed by Dave Johnson P.E.,  04/28/01]

 

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

 

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 App Note - , Mar 24th 2010]

 

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 App Note - , Robert Dobkin-Vice President-Engineering and Chief Technical Officer Sep 15th 2009]

 

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Converters:  Voltage to Current Circuits


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