4mA current regulator

can anyone offer any suggestions on how to make a simple 4mA current regulator... I started looking at LM317 voltage regulators, but found that they're gonna output a minimum of 10mA... I'm now looking at JFETs with a resistor between the source and gate... most the JFETs I'm finding can only provide currents less than 3mA...

thanks

Go and read this thread and note the posted circuits with a focus on what Eric posted. That should get you going as to a 4 mA current source.

Ron

Just out of interest, what do you need one for?

On Jun 24, 12:57*pm, panfilero <panfil...@gmail.com> wrote:
Thanks for the responses... what I'm trying to do is power an
accelerometer.... *I'm trying to re-create the "Constant Current
Signal Conditioner" side of the circuit shown in Fig. 7 of this link

**broken link removed**

but in that circuit they use a "Current Regulating Diode" I don't have
one of these, but I do have an electronics store down the street, so
basically that's what I'm trying to re-create, and for the
accelerometer I have, the current would have to be regulated to 4mA...
thanks

So you are trying to supply ~4ma to the open drain of the built-in FET, where the drain voltage is near 10V.

What is your supply voltage? They show about 20V.

yes, I'm trying to supply 4mA to the top leg of the fet (I'm not very clear on how these things work or why). I called the people who make this accelerometer and they said 4mA constant current, and the VDC power at about 24V would be good... one thing I don't understand about this circuit is... if they have 18-30V in series with a diode on one leg, and there's another parallel leg with a Volt-meter on it, how is that meter reading 10V ? I thought the idea in parallel things was that the voltage across two parallel legs would be the same...

thanks

RCinFLA said:

Current mirror - Wikipedia, the free encyclopedia

Click to expand...

Using RC's suggestion:

You will likely need additional amplification, and some filtering. Note that a variation of 10uA produces about 0.5V out.