• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 49 subscribers
  • Views 469 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

OPA2333: OPA2333P TINA-TI spice model drawing unusually high input currents (mAs!!!) in the TINA-TI simulator

Yemi Obisesan
Prodigy 20 points
Part Number: OPA2333
Other Parts Discussed in Thread: , OPA379

Hi,

 

I'm trying to simulate the OPA2333 op-amp and I used the OPA2333P model from https://www.ti.com/lit/zip/sbom166 since I couldn't find the OPA2333 model. The issue I’m having is that the OPA2333P model isn’t behaving as expected (please see below).

 

Using the OPA2333P model the current flowing in the op-amps’ input terminals is very high at 32mA! It should be close to 0A (i.e. pAs or nAs). Can anyone help explain this behaviour?

 

 

I tried a different op-amp (OPA379) and the current flowing in the op-amps’ input terminals is negligible (pA) as expected.

 

 

Regards,

 

Yemi

  • 0
    Guru 140200 points

    Hi Yemi,

    a chopper OPAmp does not work this way. The input pins must not have so much different input voltages. A chopper OPAmp will only work as expected when the feedback loop is closed and the OPAmp can make the input pins have equal potential. For the same reason a chopper OPAmp cannot work as a comparator.

    The simulated huge input currents can be caused by the model itself, as a warning, to tell you that you have made a mistake.

    Close the feedback loop and everything is fine:

    Kai

  • 0
    TI__Guru 61340 points

    Yemi,

    OPA2333 is an op amp and NOT a comparator and thus it should not be used in an open-loop configuration you attempt to do.  Using it properly in the close-loop configuration, inverting or non-inverting, show correct values for IB - see below.

    The reason for the very high input bias current, IB, in your setup of OPA2333 is that it is a chopper amplifier that includes back-to-back parasitic diodes between the input terminals, which get forward-biased when you apply 1.6V differential voltage between the input terminals - see below - whereas, OPA379 is not a chopper and thus it has no said diodes and for this reason its IB remains low.

    OPA2333_IB Circuit.TSC