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LM13700 sim in TINA-TI help!

Discussion in 'General Electronics Discussion' started by bobtech, Apr 14, 2017.

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  1. bobtech

    bobtech

    10
    1
    Apr 14, 2017
    Hi all,

    I'm trying to get a VCO circuit using an LM13700 up and running.

    It's a bog standard spec I'm trying to simulate, which I couldn't get going in LTSpice first off, so I tried TINA TI, but still to no avail. Has anyone any ideas?

    lm13700 result setup.png

    lm13700.png


    lm13700 result.png
     
  2. Audioguru

    Audioguru

    3,085
    692
    Sep 24, 2016
    If The old LM13700 IC is still available then why not build and test the circuit instead or trying to simulate it?
     
    Arouse1973 likes this.
  3. bobtech

    bobtech

    10
    1
    Apr 14, 2017
  4. bobtech

    bobtech

    10
    1
    Apr 14, 2017
    I also tried to simulate the ramp/pulse vco from the datasheet, and still getting the same issue, any ideas anyone? I've even put in initial values, but to no avail.

    [​IMG]

    [​IMG]
     
  5. Audioguru

    Audioguru

    3,085
    692
    Sep 24, 2016
    The squarewave has offset voltage because it comes from the emitter of the output darlington that has no negative feedback. The darlington has two base-emitter voltage drops.
     
  6. Arouse1973

    Arouse1973 Adam

    5,165
    1,087
    Dec 18, 2013
    What was the problem you had in LT Spice?
    Thanks
    Adam
     
  7. bobtech

    bobtech

    10
    1
    Apr 14, 2017
    I see, thanks :)




    I was getting the same flat output, as I attached in my first post.



    Managed to crack the issue

    So first thing I did was just go 100% as per data sheet, so all values are the same as above, except the supply voltage was changed from +/-9 to +/-15..

    I took out the initial conditions and simulated.... nothing

    Then I put an initial condition on the pulse o/p, and it came to life !!
    As per values of the datasheet, it was oscillating at about 37 MHz so any sort of Vc above 1 volt resulted in saturation again....

    I changed Rc and C and have it oscillating in the KHz range...

    It also allows the supply votage to be dropped again to +/-9V

    [​IMG]


    [​IMG]
     
    Last edited: Apr 15, 2017
    Arouse1973 likes this.
  8. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
    651
    May 8, 2012
    Whenever simulating oscillators in Tina always select "Use Initial Conditions" or "Zero Initial Values".

    BTW ... Welcome To EP!
    Chris
     
  9. bobtech

    bobtech

    10
    1
    Apr 14, 2017
    Thaks CD :)
     
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