OPA858:

Hi Giora,

Can you get it to work in a simple circuit? First do a DC verification to verify voltage ranges are maintained. Sometimes models will crash if they are operated outside their nominal ranges.

Best regards,

Sean

I did it., and it is not working.

A simple positive gain of 7 - the d v shows 131mv on the negative input when it should be 0.

Giora

Hello,

Even in DC I got wrong voltages.

Giora

Hello Giora,

   I was able to get the same AC and Transient simulations on the Microcap simulation software using and compared to the reference design of the OPA858 on Tina-Ti. I have attached my simulation setup and my .cir file below.

Thank you,

SimaOPA858Test.cir

Hi Sima,

I see it is working. But I do not understand why you had to float the inputs on 2.5V.

Transient is not working.(see attached)

You can also see that the voltage on the + input is not equal to the - input. (see attached)

Regards,

Giora

Hi Giora,

   I was able to get the same transient simulation by using a sin source rather than a voltage source. I have never used micro-cap simulation software until this post, so I am not familiar with the reason this difference occurs between the two different sources. I am also unsure how to make the input sin wave look more uniform as it would in Tina-TI. However, it does not seem to be a model problem, but rather with the uncertainty in choosing and setting up the input sources in this software. I also get the same voltages at both inputs of the amplifier. I have the inputs referenced to mid-supply (2.5V) rather than ground because I was following both the provided Tina-Ti reference design as well as the set-up used to obtain the datasheet specs. It is not necessary to follow this same set-up. I have attached my setup and simulation below.

Thank you,

Sima

Hi Sima.

I did the same as you did.(see attached) and it still not working.

Maybe my opa858 spice model is not the same as you have.

Can you send me the spice model (.lib)?

Hi Giora,

  From looking at your attached circuit, I believe you would need to change your voltage source to a sine source which I found by going to the component tab, selecting Analog Primitives, then selecting Waveform sources, and clicking on sine source. I found the spice model (.lib file) by going to the design and development tab of the OPA858 and downloading OPA858 TINA-TI Spice Model (Rev. B). I have attached both circuit and .lib files below.

Thank you,

Sima

OPA858.LIB

6303.OPA858Test.cir

Hi Sima,

Used your circuit and lib.

It still does not work.

Maybe something us wrong in my MC12 software.

I am using:

Hello Giora,

  I have Micro-Cap 12.2.0.2 (64 bit) which is very close to your version, so I am not sure if that is the issue. This is how I imported the .Lib File:

1. I clicked on the Windows tab at the upper left corner of the software

2. Selected Component Editor 

3. Selected Opamp_subckt_5 under Subckts (12) on the right side of the screen

4. Changed the name from Opamp_subckt_5 to OPA858 (make sure to start a new circuit file or delete the OPA858 before doing this or it will give a duplicate name error)

5. I changed the pin names to match the sub circuit definition by double clicking on each pin (1,2,3,4,5) and changing it to (INP,INN,VCC,VEE,OUT)

6. I then clicked on Import Wizard which is located the left upper tab within the component editor window.

7. For the file section, I browsed and selected the OPA858.lib file, and pressed next and finish without changing anything else. 

After completing this steps, the software will allow you to place the OPA858 symbol as part of your schematic. 

Let me know if this was any different from how you imported the .lib file.

Thank you,

Sima 

Hi Sima,

Tried your way. Still does not work properly.

Giora

Hello Giora,

  Can you show me your transient simulation with a maximum run time 10u at nodes 2 and 5 with the sine source set at A = 100m and F = 1Meg with the latest .cir file I sent you earlier?

Thank you,

Sima 

Hi Sima,

Here it is:

Hello Giora,

   The input signal seems correct, but like you pointed out before, you are not getting 2.5V at node 3 which is very unusual. Would you be able to send me your circuit file and also a snippet of OPA858 component description by double clicking the op amp in the schematic? I have attached my OPA858 component description.

Thank you,

Sima

Hi Sima,

Thanks for your patience.

Here what I have found:

1. When using a spice model with the result that I sent - the component description is:

and the spice model is (part of):

2. I change the lib file with the new downloaded from TI:

and now it is the same as in yours.

But to my surprise -when running the simulation I got an error:

Regards,

Giora

Hello Giora,

   I was looking for those sequence of lines in the snippet you shared, and I was not able to find them in the OPA858.lib file I sent you earlier. My OPA858.lib also has this at the start of the file which does not match the snippet you shared. 

     I have attached the OPA858.lib file to this post. Let me know if you find these same differences again.

Thank you,

Sima 

5126.OPA858.LIB

Hi Sima,

I am attaching where the error is:

It is the same.

Also I compared the two files and there us no difference !

Regards,

Giora

PS - How can I send you the file?

Hi Sima,

Also when I chose info -see below - the file is not exactly as the opa858.lib:

Hi Giora,

   You can send a file by clicking on insert file (paperclip icon) within the upper part of the reply window. Thank you for sharing how to access the opa858 information within the software; my file information does not have opa858 placed in random parts of the file which I have shown below. Thank you for also sharing a marked comparison of the files; I am unsure the reason you would be getting an error. The only difference I could find between our setups would be the netlist file being filled with the word opa858 at the end of most lines. Would you be able to send me the image of the error message or does the software just point to that line without any explanation?

Thank you,

Sima 

Hi Sima,

1. The software just point to that line without any explanation.

here it is. (When I erase this line and run transient again I got another error line.

the end of opa858.lib:

The end of info is:

Hello Giora,

  Sorry for the delay in response, would you be able to send me your .cir file? I looked at the end of my model info and it matches the snippet you shared. I am very unsure the reason the netlist on your end is giving you an error.

Thank you,

Sima