Hi, i am looking for a current source in the range of nano amperes, my working current range is 10n Amp to 500n Amp of current source. I saw you provide an IC REF 200 but the output current of this ic is still high for my application. Do you have any solution regarding my application. Or any idea how i can use REF 200 to get an output in my desired range.
Thank You
Hi Mannan,
Enclosed are links about how to build V to I converter.
https://www.ti.com/lit/an/sbva001/sbva001.pdf
https://www.ti.com/lit/ug/slau507/slau507.pdf
The REF102 and REF200 are legacy devices, and I am not sure that they will work well for your current range. BTW, How precisely do you want your 10nA to 500nA in current source?
I found the following current source circuit that might work for your application. It claimed that it has <10pA error out of 1nA in accuracy (total error < 1%). I have not had a chance to simulate in Tina. If you are interested, please let me know. We may have to use lower Vos and higher precision op amp to achieve the precision in the current source application.
Alternatively, you may build current source out of discrete matched Mosfets or BJTs in current mirror circuits, which are used inside of IC or REF200. Because of the low current levels, it may be more difficult to make it practical with discrete components.
Best,
Raymond
Hi Mannan,
Here is a working version of 10nA to 500nA constant current source with total error <1%. I changed the circuit with OPA192 instead of OPA376, though both op amp are equally comparable (no particular good reasons for the change, both will work for your application).
The current load R11 has to be <= 1/1000 of R10 or 10MOhm in order to keep the error low. Vin needs to be from 100mV to 5V in range to generate 10nA to 500nA output current.
Enclosed is the Tina simulation.
If yo do not like -2.5V negative rail, you may use LM7705 to generate -0.232V from positive regulator voltage, see the simulation below.
If you have any additional questions, please let us know.
Best,
Raymond
