OPA659: Question about current noise

It might, but who cares at that level. The noise gain shape normally will make the voltage noise contribution dominant

Hi George,

can you post a schematic?

Kai

I see this plot in the OPA859, certainly a designer sim and not likely in the TINA model,

TheOPA659 might be similar but only a designer sim would tell, 

The plot in the OPA859 data sheet is what prompted me to ask the question.  It is not clear to me if it applies to CMOS transistors only or if it applies to JFETs as well.  Figure 22 in the OPA659 data sheet shows the current noise constant up to 10MHz, which is different from the way it varies in the OPA859, so I suspect the OPA859 figure does not apply to the OPA659.  Is there any way of finding out how the OPA659 behaves to within an order of magnitude?

Thanks

Hello George,

The plot on the OPA859 datasheet is a more accurate representation of how the current-noise will behave on the OPA659.

Best,

Hasan Babiker

If that is the case, the OPA659 data sheet is way off because it shows a current noise of 1.8fA/rtHz at 10MHz whereas the OPA859 has ~0.8pA/rtHz at 10MHz.  Which one am I supposed to believe?  Or are they both wrong?

Hello George,

I will look more into this and get back to you.

Best,

Hasan Babiker

Hello George,

Please use the 1.8fA/rtHz of the OPA659 as an initial flatband number of the current noise that will rise over frequency. Current noise at 10MHz will be closer to the magnitude of the OPA859 rather than 1.8fA/rthz.

Best,

Hasan Babiker