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Original question:

OPA835: OPA835 simulation

OPA835: Input bias current

Valerian Kuechle
Prodigy 10 points
Part Number: OPA835
Other Parts Discussed in Thread: PSPICE-FOR-TI, TINA-TI, OPA836

When I model a test amplifier using a OPA835 in Ti-Pspice the simulated input bias currents are too high, around 10ua. If I model the same circuit in TinaTi the currents are in the 100na range, which is in the normal range. What do I have to do to get Ti_Pspice to give the correct output. I believe the problem is in the spice file.

  • +1
    TI__Genius 17226 points

    Hi Valerian, They look like two different netlists to me. But the PSPICE-for-TI model's bias current isn't 10uA for me? It still looks reasonable. If you really want, you can download the netlist from the TINA-TI model and import it as a third party model into PSPICE-for-TI, but maybe something else is a bigger issue here.

    opa835-2021-11-11T21-17.zip

  • +1 in reply to Sean Cashin
    Prodigy 10 points

    That circuit works as expected for me as well.. The following one does not, however with a OPA836 it behaves as expected. I want to use the OPA835 because of its low Iq drain. The OPA835 Ibias does not seem to model correctly on a gain of 10 non-inverting amplifier either.

  • 0 in reply to Valerian Kuechle
    TI__Genius 17226 points

    Hi Valerian, I have verified your finding. The bias current seems to become higher with a mid-supply ≠0V. If you change V1 to 1.8V, and the ground to -1.8V, the bias current does go back to normal. When we moved all of our models from TINA-TI to PSPICE-for-TI, there where a few models that did not work at all for single-supplies, not balanced around zero. This one seems to work, but the bias current is affected. I will see about fixing it, but in the meantime, are you able to just simulate the amplifier with Vcc=1.8V and Vee=-1.8V?