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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) |
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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) |
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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) |
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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) |
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60 MCurrent Source Feeds Telecomm Lines - 12/12/97 EDN-Design Ideas:
(design idea) |
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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) |
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A Simple Current-Sense Technique Eliminating a Sense Resistor AN-7 -
Application Note 7 from Microsem (app note) |
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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) |
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AN-1244: Photo-Diode Current-To-Voltage Converters - National
Semiconductor Application Note (app note) |
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AN-240: Wide-Range Current-To-Frequency Converters - National
Semiconductor Application Note (app note) |
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AN-D16: Lnd1 Series: Constant Current Sources And - Supertex
Semiconductors (app note) |
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AN-D18: Dn25 Series: Constant Current Sources And - Supertex
Semiconductors (app note) |
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Basic Current Source - Circuit Ideas for Designers Application
Notes Advanced Linear Devices, Inc. (app note) |
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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) |
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Bipolars Provide Stable Current Source - 09/24/98 EDN-Design Ideas:
(design idea) |
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Buffered Current Source - Circuit Ideas for Designers Application
Notes Advanced Linear Devices, Inc. (app note) |
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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) |
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Cascode Current Source - Circuit Ideas for Designers Application
Notes Advanced Linear Devices, Inc. (app note) |
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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) |
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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) |
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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) |
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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) |
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Constant Current Amplifier - (electronic diagram) |
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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) |
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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) |
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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) |
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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) |
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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) |
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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) |
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Current Source & Sink Circuits Have Low Tc - 07/04/96 EDN-Design
Ideas: (design idea) |
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Current Source Allows Measuring Three Wire Rtd - 07/06/00 EDN-Design
Ideas: (design idea) |
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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) |
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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) |
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Current source has high compliance - 09/01/00 EDN-Design
Ideas:.....(design idea) |
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Current Source has High Output Impedance - 06/22/00 EDN-Design
Ideas:.....(design idea) |
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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) |
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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) |
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Current Source Mirror - Circuit Ideas for Designers Application
Notes Advanced Linear Devices, Inc. (app note) |
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Current Source Multiplication - Circuit Ideas for Designers
Application Notes Advanced Linear Devices, Inc. (app note) |
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Current Source with Gate Control - Circuit Ideas for Designers
Application Notes Advanced Linear Devices, Inc. (app note) |
