PSPICE-FOR-TI: How to do Noise Analysis in PSpice for TI ?

Kristian Ougaard

Part Number: PSPICE-FOR-TI

I have designed an amplifier with discrete transistors which are neither in the PSpice nor TI library and want to analyse the noise performance. The circuit works fine in normal AC analysis and I can add between one and three Vdb markers and see the frequency response, so far so good.

I then enable the Noise Analysis in the simulation profile and specify the output voltage, input source and number of intervals. All markers are removed from the schematic as you usually would pick the noise voltages from the Add Trace window in Probe. When you click the simulate icon the ORCAP_15098 message is shown preventing the simulation from running.

Then, when adding a voltage marker to the circuit, this voltage is correctly displayed. In the Add Trace menu only a few (8) node voltages are listed to choose from. Normally you would see the full circuit list including currents and powers. The Noise check box cannot be ticked even though the Noise Analysis is enabled in the simulation profile??

How should noise analysis be done in PSpice for TI. Maybe there is another way of setting up the system, or is this a major limitation of the program.

Hoping that there is a solution to this.

Regards

Kristian

over 2 years ago

0 Pinninti Reddy over 2 years ago

TI__Prodigy 90 points

Hi Kristian,

Kindly look into the below link

https://e2e.ti.com/support/tools/sim-hw-system-design/f/simulation-hardware-system-design-tools-forum/969665/faq-pspice-for-ti-why-can-t-i-plot-more-than-three-signals-in-pspice-for-ti

Thanks

0 Kristian Ougaard over 2 years ago in reply to Pinninti Reddy

Prodigy 20 points

Hi Pinninti

Thanks for your answer.

However, I fully understand that the limitation of PSpice for TI will only allow you to see a maximum of 3 voltage probes at any given time.

So my question is how do I get a single noise voltage to be displayed ?

Usually you only need the noise voltage canlulated on the output of the amplifier.

Regards

Kristian

0 Jackie Horn over 2 years ago in reply to Kristian Ougaard

TI__Expert 5880 points

Hi Kristian,

For noise simulations, please open the simulation profile settings in PSpice for TI. Choose the tab for Data Collection, and make sure that you have set either "All but Internal Subcircuits" or "All"

Yes, there is a limitation here on 3rd party models here. You can get around this by using the built-in modeling application: https://e2e.ti.com/support/tools/simulation-hardware-system-design-tools-group/sim-hw-system-design/f/simulation-hardware-system-design-tools-forum/973740/faq-pspice-for-ti-can-i-define-my-own-model-in-pspice-for-ti

Please let me know if you have further questions. Thank you,

Jackie

0 Kristian Ougaard over 2 years ago in reply to Jackie Horn

Prodigy 20 points

Hi Jackie,

Thanks for your answer.

In the Data Collection tab Voltage, Current, Power, Digital and Noise are all set to "All but Internal Subcircuits". Still only about 8 voltages are shown in the Add Trace drop down box, not all!

In my initial question I tried to explain the problem I see:

- The Noise Analysis checkbox is checked in the simulation profile and all three parameters are filled in.

- Clicking the simulation icon will not run the simulation without any marker/probe attached in the circuit diagram, ERROR ORCAP_15098. (It would have been better if you could run the simulation without any probes and use the ADD Trace to select a max of 3 traces from the full list.)

- After adding a Voltage probe to the output of the amplifier the simulation will run and display the voltage correctly. However. it is not possible to use the "Add Trace" and select a noise voltage - you cannot select the Noise checkbox!

Using the built-in modeling application, I tried to add a PSpice NPN transistor and then modify its parameters as shown in your above link. However, the "More..." → "Edit PSpice Component" cannot be selected so you are not allowed to edit the model!

Hmm, what can I say. I think that PSpice for TI has more limitations than just that of the three markers.

Regards

Kristian

0 Jackie Horn over 2 years ago in reply to Kristian Ougaard

TI__Expert 5880 points

Hello Kristian,

If you would like for me to take a deeper look, please feel free to share your project here. You can find sharing instructions here: https://e2e.ti.com/support/tools/simulation-hardware-system-design-tools-group/sim-hw-system-design/f/simulation-hardware-system-design-tools-forum/969692/faq-pspice-for-ti-how-do-i-share-pspice-for-ti-projects

Thank you,

Jackie

0 Kristian Ougaard over 2 years ago in reply to Jackie Horn

Prodigy 20 points

Hi Jackie

As I cannot share the low noise amplifier design, I made a totally new very simple two transistor amplifier to check whether I get the same restrictions as before. This simple circuit can easily be simulated and shows the frequency response using the Vdb marker on the output.

However, all the restrictions I have described previously show up again. As there is no Vnoise marker available and the simulation will not run without any marker in the schematic, it is not possible to simulate the noise at the output of the amplifier. You cannot enable the Noise check box in the Add Trace menu even though Noise Analysis is enabled in the simulation profile.

I have made an archive of the project and it is attached below.

I hope you are able to find a solution - thanks

Kristian

TestAmp-2021-09-01T12-23.zip

0 Jackie Horn over 2 years ago in reply to Kristian Ougaard

TI__Expert 5880 points

Thank you Kristian. I will let you know my findings.

0 Kristian Ougaard over 2 years ago in reply to Jackie Horn

Prodigy 20 points

Hi Jackie

Have you found a solution to this problem?

Regards

Kristian

0 Jackie Horn over 2 years ago in reply to Kristian Ougaard

TI__Expert 5880 points

Hello Kristian,

I am able to observe what you have described. However, the restrictions are triggered by the custom models included in your library. If you would like to include pnp or npn devices and view all of their waveforms, you can search the PSpice for TI library for pre-built models. The pre-built models will not trigger any restrictions. See examples below:

PSpice for TI was created as an easy method for our customers to access and simulate the TI product portfolio. If you are seeking a more powerful simulator to create your own models or devices, we would recommend Cadence SBP. Cadence Design Systems is the developer for both PSpice for TI and SBP, but SBP is more powerfully equipped.

Thank you,

Jackie

0 Kristian Ougaard over 2 years ago in reply to Jackie Horn

Prodigy 20 points

Hi Jackie

Thanks for your answer!

I highly appreciate that TI offers a version of PSpice as a free tool and only with a few limitations. I happened to run into one of these limitations with noise simulation of a transistor circuit using a full library transistor model. At least I now know, that I did not do anything wrong in the simulation setup.

OK Jackie - thanks for your help.

Regards

Ktristian

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PSPICE-FOR-TI: How to do Noise Analysis in PSpice for TI ?