Hi everybody, 
Recently, I use OPA129 to design a I/V converter for a current as big as 10-100pA. But I found the Ibs of OPA129 is stable on 16 pA, which is very different with 100 fA on its datasheet. This result comes from a NI Multism simulation.
So I feel very curious about weather there is someting wrong in my circuit or OPA129 is originally not suitable for the ultra low current measurement. Looking forward to your kind help.