Error in OPA129 model

[shiiuen]

Hye,

I'd like to repot a error (at least what i think is a error) in the embeded spice model of NI multisim for
OPA129(Ultra-Low Bias Current Difet(R) Operational Amplifier).

I used TI OPA129 op-amp to built a current-to-voltage convertor as the attachment. However, while I simulated
the circuit, I found that the current flowing through the input footpin of op-amp is far higher than the current
flowing through feedback resistor R4, even using a proper feedback resistance.

After excluding the other possible problems, I check the spice model of OPA129, I found that the input resistor(Ri)
in spice model of OPA129 is as smaller as 1e-9 ohm, this is incredible beacuse operational amplifier usually has a huge
input resistor. I also checked datasheet of OPA129, in which the input impedance is at least 1e13 ohm
(You can browse the data sheet at http://www.datasheetcatalog.org/datasheet/texasinstruments/opa129.pdf).

And then I am aware of that there are similar errors in the following model

Component: OPA129U
manufacturer/ID: IIT/OPA129,IIT/OPA129_3,IIT/OPA129P

Component: OPA129UB
manufacturer/ID: IIT/OPA129,IIT/OPA129_3,IIT/OPA129PB

I had posted the screenshots and design files of the current-to-voltage convetor for your check.

BTW:

I noted that Ti provides spice model of OPA129 in the format of PSpice and TINA-TI spice,
I would like to know how to import them into NI multisim?

[Tayyab_R]

Hi shiiuen,

I am looking into the models which you reported that are not working properly. As far as importing spice models, Multisim supports pspice so what you can do is follow the procedure given in the following link to create a custom component and apply a pspice model to the component.

http://zone.ni.com/devzone/cda/tut/p/id/3173

Hope this helps.

[shiiuen]

thanks, that solve the problem properly.