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Current Reference IC for V & C Reference Standard Box
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t1d:
I am designing a Voltage and Current Standard Reference Box for calibrating hobby-grade test equipment... I have settled on the MAX6350 for the voltage side... Super 0.02% accurate, right out of the box... But, I am not finding an equally great current reference... I mostly see the REF200, but it only has a 0.5% accuracy... The LT3092 is even less accurate... I was hoping for more... Suggestions? Please and thank you.
David Hess:
Current references usually rely on the voltage reference and a precision resistor.
graybeard:
Use a zero drift op-amp, a precision low TC resistor, and a fet.  Connect the gate of the fet to the output of the opamp.  Connect the non-invering input of the op-amp to your voltage reference.  Connect thr invering input to the source and the resistor.  Connect the other side of the resitor to the rail connected to the other side of the reference. The current output will be the drain of the fet.  You can use a enhacement or depletion mode mosfet, or a jfet depending on circuit node voltages.  Use a p-channel device if you want the current source to be on the high side, or an n-channel device if you want it on the low side. 

You can also use a npn or pnp bipolar, but there will be a slight error becasue of the base current.  gate --> base   source--> emitter  drain --> collector (output)

If I am not concerned about fine accuarcy I usually use a bipolar.  It is your choice depending on your needs.

Since for loop gain the fet or bipolar is being operated as a source (or emitter) follower, the op amp loop remains stable so long as you uas a slow (<4 MHz) unity gain stable op-amp.
Vgkid:
 What sort of accuracy are you trying to achieve, bipolar?
Heres a good look.
https://www.eevblog.com/forum/metrology/recycling-of-precision-current-source-noise-reduction-for-low-burden-shunts/

https://translate.googleusercontent.com/translate_c?depth=7&nv=1&rurl=translate.google.com&sl=auto&sp=nmt4&tl=en&u=http://bbs.38hot.net/forum.php%3Fmod%3Dviewthread%26tid%3D17593%26extra%3Dpage%253D9%26mobile%3D2&usg=ALkJrhiXe_Y6jtKzAUMGsriO3sWrwgY0Jw
t1d:

--- Quote from: David Hess on March 31, 2020, 02:18:19 pm ---Current references usually rely on the voltage reference and a precision resistor.

--- End quote ---
Well, even with my limited skills, that approach had come to mind. Good thinking. I appreciate your input.
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