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  • TI Thinks Resolved

TINA/Spice/THS4271: Single-supply vs Dual supply AC Simulation Differences??

Prodigy 60 points

Replies: 5

Views: 158

Part Number: THS4271

Tool/software: TINA-TI or Spice Models

I am getting differences in the simulation when using single-supply vs dual supply.

I tested with the THS4271, and OPAx828 TINA-TI Spice Models.

The OPAx828 shows the same gain/phase results for single supply and dual supply.

The THS4271 shows strange results for single-supply, and strange phase for dual-supply (but good gain)

I compared these "open-loop" simulation results with the datasheets, and the OPAx828 is perfect in line with the datasheet.

The THS4271 just seems...wrong. Like there is a problem with the SPICE model.

What do you guys think?

#1THS4271
VDD = 10V, V+ pin Vref is 5V (Vos and Vcm etc should be fine)

#2THS4271
VDD = ±5V, V+ pin Vref is GND (Vos and Vcm etc should be fine)

#3 OPAx828
VDD = 10V, V+ pin Vref is 5V (Vos and Vcm etc should be fine)

#4 OPSx828
VDD = ±5V, V+ pin Vref is GND (Vos and Vcm etc should be fine)

 SingleSupply-OpenLoopGain-AC.TSC

  • Hi Darren, 

    I have seen the behavior you are seeing in plot #1 before. It seems to be an issue with how the simulator is solving the circuit for certain configurations. My first suggestion would be to change the analysis parameters by opening the Analysis->Set Analysis Parameters menu. Then click the hand symbol in the bottom right of the window and select open. This should open to a default directory and at the bottom you should find several pre-set parameter (.PRM) files. Try the "DC Convergence of nonlinear circuits" or the "Irregular circuit problems caused by floating nodes" and see if that helps. 

    Regards, 

    Jacob Freet 
    High Speed Amplifiers

  • In reply to Jacob Freet:

    Hi Jacob, I am sorry my reply is so late in coming.

    I have tried the .PRM file you suggested, but keep seeing the same waveform.

    This is when using the AC sweep by the way.

  • In reply to Darren (FAE):

    Hi Darren, 

    Yes, unfortunately sometimes it can be tricky to get the AC response to behave properly. I would suggest trying some of the other .PRM files that are available and seeing if any of them help. If you attach the TINA file, I can also try and resolve the issue. 

    Regards, 

    Jacob Freet 
    High Speed Amplifiers

  • In reply to Jacob Freet:

    Hello Jacob,

    I attached the model in my first post, but I guess it was in a pretty inconspicuous place.

    Here it is again.

    Any insights would be greatly appreciated!

    Thanks!

    2438.SingleSupply-OpenLoopGain-AC.TSC

  • In reply to Darren (FAE):

    Hi Darren, 

    Apologies for missing you attachment. This is actually an easy fix. If you switch the simulation to run on +/- 5V supplies with ground as your input voltage then it will work. A lot of our older models were designed with split supply simulations in mind and sometimes run into some errors when running in single supply mode. We are working to update the catalog with newer models, but unfortunately it will take some time to renew each device. Until then you can just shift your supply voltages to make it a split supply and it should work. 

    Regards, 

    Jacob Freet 
    High Speed Amplifiers

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