i would like to measure very small current (.1 uA - 20 uA) and the output voltage limit is 6 volt. is the attached circuit ok for this??
Thanks
Thanks
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i have INA121 and it says bias current as low as 4 pA. if i want to use it for the purpose, do i need any other modification???The 358 has quite a bit of input bias offset so you might want an instrumentation amplifier.
i wanted to use woth available one....currently i have ina 121, AD823, lm 393....seems like ina121 would be suitable...To keep the error down to 1% you need an input current of 1 na or less. www.mouser.com shows 2018 op-amps that can do that. (Use the search engine on a vendors site.)
i did not test it yet. i think i would connect it to the negative terminal of source (current source) . is there any problem to do that??What does the ground symbol connect to? That is importaint for the common mode voltage.
What TWO points do you use to measure U1A-1 (the op amp output)?
You may want to study Mr David Jones' design against yours. He gives a very clear explanation for each one of the components. He's also got a YouTube channel that you may want to check out. See attached file.i would like to measure very small current (.1 uA - 20 uA)
The INA121 is an instrumentation amplifier and is not suitable. They have internal feedback circuits and normally are not used with any external feedback.i wanted to use woth available one....currently i have ina 121, AD823, lm 393....seems like ina121 would be suitable...
by Jake Hertz
by Aaron Carman
by Aaron Carman