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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 added
11/05) |
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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 added 7/02) |
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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. (added 12/04) ….(designed by David A. Johnson) |
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60 MCurrent Source Feeds Telecomm Lines - 12/12/97 EDN-Design Ideas: (design idea
added 3/03) |
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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. (added 12/04) ….(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 added 6/06) |
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Amplifier & Current Source Emulate Instrumentation Amplifier - 11/13/03 EDN-Design
Ideas: The classic threeor 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 added 12/04) |
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AN-1244: Photo-Diode Current-To-Voltage Converters - National Semiconductor
Application Note (app note added 2/06) |
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AN-240: Wide-Range Current-To-Frequency Converters - National Semiconductor
Application Note (app note added 2/06) |
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AN-D16: Lnd1 Series: Constant Current Sources And - Supertex Semiconductors
(app note added 2/06) |
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AN-D18: Dn25 Series: Constant Current Sources And - Supertex Semiconductors
(app note added 2/06) |
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Basic Current Source - Circuit Ideas for Designers Application Notes Advanced
Linear Devices, Inc. (app note added 6/06) |
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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 added 02/07) |
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Bipolars Provide Stable Current Source - 09/24/98 EDN-Design Ideas: (design idea
added 3/03) |
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Buffered Current Source - Circuit Ideas for Designers Application Notes Advanced
Linear Devices, Inc. (app note added 6/06) |
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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 added 11/05) |
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Cascode Current Source - Circuit Ideas for Designers Application Notes Advanced
Linear Devices, Inc. (app note added 6/06) |
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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 added 1/05) |
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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
added 08/08/08) |
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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 added 03/03/03) |
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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 added 6/03) |
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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 added 7/02) |
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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 added 08/09) |
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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 added 1/05) |
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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.
(added 12/04) ….(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 added 9/07) |
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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 added 02/09) |
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Current Source & Sink Circuits Have Low Tc - 07/04/96 EDN-Design Ideas: (design
idea added 3/03) |
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Current Source Allows Measuring Three Wire Rtd - 07/06/00 EDN-Design Ideas:
(design idea added 2/06) |
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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 added
1/05) |
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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 added 01/05) |
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Current source has high compliance - 09/01/00 EDN-Design Ideas:.....(design idea
added 11/05) |
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Current Source has High Output Impedance - 06/22/00 EDN-Design Ideas:.....(design
idea added 11/05) |
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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 added 1/05) |
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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 added 09/08) |
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Current Source Mirror - Circuit Ideas for Designers Application Notes Advanced
Linear Devices, Inc. (app note added 6/06) |
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Current Source Multiplication - Circuit Ideas for Designers Application Notes
Advanced Linear Devices, Inc. (app note added 6/06) |
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Current Source with Gate Control - Circuit Ideas for Designers Application Notes
Advanced Linear Devices, Inc. (app note added 6/06) |
