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noise source

spanika kamuni
Intellectual 370 points
Other Parts Discussed in Thread: TINA-TI, OPA227, OPA627

hii all,

i want to inject noise into my circuit from 2 inputs(specifications +-5V, crest factor 5). I have checked that the noise voltage source and noise current source provided in TINA generates noise, but how can I edit their macros according to my own specifications. Everytime the macros are edited to match the data sheet of op amp. 

I wanted to know if I can really use these noise voltage and current sources to generate noise as per my requirement. If not can you please suggest me a way to insert noise into my circuit.

  • 0
    TI__Guru* 93105 points

    Hello Spanika,

    If you are using the free version of TINA-TI, I think there is a resource that can be of use to you. Start TINA-TI and select:

    File > Open Examples > Noise Sources > TINA Noise Sources revC.TSC

    A TINA schematic showing an OPA627/OPA227 circuit should be presented. There are voltage and current noise sources available having names such as Vn1 Vnoise and In1 In_fA that can be selected. Their noise characteristics can be found by double clicking on their symbol. A small window will open that has an "Enter Macro" button on it. Clicking on that button allows you to see and edit the PSpice code that sets the noise performance. These noise source can be copied and pasted into your TINA schematic.

    Internal to the noise model there are references to noise articles by Art Kay. The on-line journal that published Art's work closed down several years ago. I tried to find a link to it and did find one from Asia that provides some of his original work:

    http://wenku.baidu.com/view/808f4df04693daef5ef73d2d.html?re=view

    I hope this is of help to you.

    Regards, Thomas

    PA - Linear Applications Engineering

  • 0 in reply to Thomas Kuehl
    Intellectual 370 points

    Hello Thomas,
    Thank you for the reply. I have already gone through all the data you refered. I do not want to make my op amp as a noise model. instead I want to give noise as one of the Inputs to my design. I cannot edit the .Param Terms in the macro since I do not have any data sheet at Hand. The tutorial always Edits the macro based on the noise curves in the data sheet of a particular op amp.
    my question is, if I can really use these noise voltage and noise current sources to send a user defined noise into the System. Do you have some option in TINA like adding a random noise source(RND function) like in pspice. This was the design I was talking about. I want to give in noise1 and noise2. I am using free Version of TINA.

  • 0 in reply to spanika kamuni
    TI__Guru* 93105 points

    Hello Spanika,

    I searched through the TINA Spice documentation on line and didn't find any reference to the RND function you mention. It appears that became available in later revisions of Cadence like 16.6, so it appears to be a more recent addition to that simulator.  It appears that TINA doesn't support the function at this time.

    I did find a discussion on the Webench Tools E2E forum that discusses a noise simulation need that sounds very similar to yours. It discusses utilizing the PWL waveform capability of a signal source to produce an input somewhat noise-like. I realize that isn't exactly what you are after, but maybe it would give you something to try as an alternate:

    https://e2e.ti.com/support/development_tools/webench_design_center/f/234/p/135362/487765

    Regards, Thomas

    PA - Linear Applications Engineering

  • 0 in reply to Thomas Kuehl
    Genius 3295 points
    Hi,

    I don't use TINA very much; I use LTSpice for general sims. One of the techniques we use to inject noise is to "stack" sources. To do what you're describing, I would take the noise source and attach it to the ground node of the signal source (noise to ground). In this way the signal is riding on the noise. Hope this helps...

    Mike T.
  • 0 in reply to Mike Tripoli
    Intellectual 370 points
    Hello Thomas,

    The link you sent doesnt serve my purpose. As Mike suggested I was using Ltspice for my Simulation earlier, but could not Import TI op amps into ltSpice. dats the reason I swiched to TINA TI; but now I face a Problem with Noise source using TINA.

    Spanika kamuni
  • 0 in reply to spanika kamuni
    Genius 3295 points

    TI has gone to using encrypted Spice models, as such, they don't work with LTSpice. This hasn't always been the case; there was a time when with a little work to the SPICE model's from TI one could use them in LTSpice. 

    That all being said, unless there is a particular feature of a certain opamp (which probably isn't in the model anyway) or other device, one can usually substitute an LT device into the sim for testing. At the end of the day, only building the circuit and testing it will tell you everything one needs to know. 

    Mike T.

  • 0 in reply to spanika kamuni
    TI__Guru* 93105 points

    Hello Spanika,

    Nearly all of our op amp models should run in TINA-TI. There may be some very old models that were developed using a different simulator that will have a problem in TINA. Many of TI's non op amps models are encrypted, but the majority of the op amp models are not. The encryption can be an issue with non-TINA simulators. Some of our op amp models don't run with other simulators even if they aren't encrypted. It usually comes down to subtle syntax differences that aren't compatible between simulators. 

    The noise models and our op amp models should be usable with TINA. There are cases when large circuits involving numerous complex models can be tough to bring to convergence. If you are attempting to run a transient analysis make sure you try the different options such as "Zero initial conditions," etc.

    Regards, Thomas

    PA - Linear Applications Engineering

  • 0 in reply to Thomas Kuehl
    Intellectual 370 points

    Gaussian noise.xlsxHello,

    I tried to make my noise source using PWL. I simply generated a bell curve in Excel and tried to put in the values into PWL but now my doubt is, the PWL takes in the values only in ascending order. If I arrange the values in ascending order my curve is disturbed. Can you please give me a Suggestion. I have attached my Excel file below.