The datasheet says + - 20fA gauranted
however the datasheet rev B page 17 shows statistical data spreading way outside this for both inputs, in fact the plot states the standard deviation is about 20fA.
Which is correct ?
I see other people were querying the bias current not meeting 20fA, but did not say how bad.
Are you referring to these histograms on page 17?
If so, these are with T = 125C which has a max limit of +/-250 fA.
The 20 fA that you are referring to is with -40C < T < +85C and I did not see any histograms for this temp range.
Please let me know if I'm not answering your question.
Hi Hooman, thanks, yes that explains it, did not notice the T.
I was hoping to find some data about what the bias current typically is, the sheet just says <1. Are you familiar with these amps ?
I think the input bias current at room temperature histogram can be estimated to have a sigma (standard deviation) of 2 fA (= 20 fA_max / 10). The factor of 10 is from looking at the the T= 125C histogram and a 250 fA max limit (sigma = 25 fA from page 17 plots).
Hi Hooman, thanks, yes intresting reasoning. I think that 2fA may be a little high because the bias current at 25C is specified as below 1fA typically.
There are plots to show how bias current changes with temperature whith temperature which show 0.1fA or below depending on supply V. I find it difficult to believe that it would be typically this low, I think since this plot primarily shows the temperature characteristic, I think a device was chosen that is nominally zero.
A histogram at 25C would be really useful.
Think I need to get one and make some measurements.