Help test a model for LTSpice; LM2907A?

Discussion in 'General Electronics Chat' started by SgtWookie, Apr 26, 2010.

  1. SgtWookie

    Thread Starter Expert

    Jul 17, 2007
    After starting and stopping on this for awhile (and getting over various learning curves), I think I've adapted a workable LTSpice simulation for an LM2907.

    Over a year ago, I stumbled across a model for an LM2907 that Russ Kincaid of Kincaid Engineering had created and posted on a website somewhere, which is now long gone. Mr. Kincaid has apparently retired, and hasn't been heard from in awhile (anywhere that I can find, that is).

    I took his .subckt LM2907, renamed it LM2907A, and used a 2N3904 for the NPN and 2N3906 for the PNP transistors he was using.

    If the input frequency is higher than the circuit is configured for, you will have strange results. LM2907A test.asc max input frequency is about 900Hz.

    The file contains:
    LM2907A.sub - put in \Program Files\LTC\SwitcherCad\lib\sub
    LM2907A.sym - put in \Program Files\LTC\SwitcherCad\lib\sym
    LM2907A test.asc - put in \Program Files\LTC\SwitcherCad

    The image file is Mr. Kincaids' concept of the "guts" of the LM2907.

    Review the notes in LM2907A.sub

    I don't have any of the LM2907/LM2917/LM2907-8/LM2917-8 IC's, so have nothing to compare them to except the formulas in the datasheet.

    However, if this turns out to be a reasonable simulation, it could be helpful for a number of folks that are trying to use this IC.
  2. kingdano


    Apr 14, 2010
    I would love to help, but never having used the device i dont know what help i could be.


    Anything rudimentary i can do to help out?

    Perhaps an app note circuit simulation?
  3. SgtWookie

    Thread Starter Expert

    Jul 17, 2007
    It's just that I've been looking at this thing for so long, I'm not the one to run it through it's paces. It's one of those situations where when you're too familiar with a circuit (or have been looking at it for too long), you overlook stuff.
  4. kingdano


    Apr 14, 2010

    read my newest post, i think we are in the same boat.
  5. ifixit

    Well-Known Member

    Nov 20, 2008
    Hi Sgt,
    I have downloaded your files and have them working. I will play around with it somemore and let you know how things go.

    Some results so far show good linearity as I step from 100Hz to 900Hz.

    Looks like 0.75 Volts per 100Hz...
    .step f=100
    .step f=200
    .step f=300
    .step f=400
    .step f=500
    .step f=600
    .step f=700
    .step f=800
    .step f=900

    step RMS(v(out)) FROM TO
    1 0.756641 V
    2 1.50383 V
    3 2.25347 V
    4 3.00454 V
    5 3.75467 V
    6 4.50558 V
    7 5.25609 V
    8 6.00652 V
    9 6.75686 V