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Anonymous Poster

How to Design a Current Injection Circuit

05/13/2009 3:30 AM

hey guys, any ideas on how to design a circuit with a current of just 1ma? thanks for you help.
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JohnDG
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#1

Re: 1ma current injection circuit.

05/13/2009 3:34 AM

1.5V cell in series1 with a 1k5 resistor.

If you need more, please explain your problem.

1 or parallel - comes to the same thing.

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Anonymous Poster
#2

Re: How to Design a Current Injection Circuit

05/19/2009 10:37 PM

i would need to DIY a circuit with only 1mA and that has a "security" catche which will keep the current at 1mA.
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JohnDG
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#3
In reply to #2

Re: How to Design a Current Injection Circuit

05/20/2009 3:45 AM

Simplest thing to do IMHO is use an LM317 regulator - see fig. 7 in this from Wikipedia. For 1mA, change the current sense resistor from 1.25Ω to 1250Ω (usually written 1k25). It only needs to be a little 0.125W or 0.25W type. Also, forget the LED & 100Ω resistor.

The input voltage can go up to 40V, which you may need to drive 1mA into higher resistance loads.

Here's the circuit from the link:

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