We think we've observed bias current drift on some THS3062 current-mode opamps, on the non-inverting input, roughly 10 uA in 6 months, systematic in one direction across multiple amps.
A regular opamp has, say, an NPN differential pair, identical transistors run at relatively low emitter and base currents.
A current-mode opamp has PNP and NPN transistor bases on the ni input, with fairly high emitter currents for speed. So the net Ib is the small difference between the largish base currents. We're conjecturing that PNP and NPN transistors might age differently, and change the net Ib.
Something like this:
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