Connect with us

Problem with .step in LTSpice

Discussion in 'CAD' started by Paul Burridge, Aug 16, 2004.

Scroll to continue with content
  1. Hi,

    I've come across an odd problem in the simplified circuit I'm posting
    to a.b.s.e under the same subject title as this message.
    I can't seem to get LT to step through 3 drain resistor values whilst
    performing a DC sweep of Vgs. It should amount to just 30 iterations
    in total, but LT is sweeping through over 22,000 when I include "oct"
    in the .step statement. I can't get it to run at all without "oct" in
    that line and I've never had to use "oct" at all for a step run
    before. Can anyone tell me if the syntax for this kind of check has
    changed recently and/or what the correct syntax should be?

    Thanks,

    p.
     
  2. Paul,
    ..step param R 1k 5k 1k ; step from 1K to 5K in 1K steps
    ..step oct param R 1K 5K 10 ; step from 1K to 5K in 10 steps per octave

    BTW, LTspice files aren't binary, they're ASCII:

    --Mike

    --- step.asc ---
    Version 4
    SHEET 1 880 680
    WIRE 368 32 368 208
    WIRE 144 80 144 32
    WIRE 144 32 368 32
    WIRE 144 160 144 192
    WIRE 144 288 144 384
    WIRE 16 368 16 384
    WIRE 16 384 112 384
    WIRE 112 384 144 384
    WIRE 368 384 368 288
    WIRE 112 384 112 400
    WIRE 96 256 16 256
    WIRE 16 256 16 288
    WIRE 144 384 368 384
    FLAG 112 400 0
    SYMBOL njf 96 192 R0
    SYMATTR InstName J1
    SYMATTR Value 2N3819
    SYMBOL voltage 368 192 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V1
    SYMATTR Value 20
    SYMBOL voltage 16 272 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V2
    SYMATTR Value 1
    SYMBOL res 128 64 R0
    SYMATTR InstName R1
    SYMATTR Value {R}
    TEXT -80 144 Left 0 !;op
    TEXT -256 448 Left 0 ;.step param R 1k 5k 1k
    TEXT -208 264 Left 0 !.dc V2 5 -5 1m
    TEXT -256 480 Left 0 !.step oct param R 1K 5K 10
     
  3. Great; thanks, Mike.
    Is there a comprehensive manual on LTS anywhere on the 'net or in
    print form that covers all the functionality of the program? A help
    file alone doesn't really do it justice.
     
  4. Paul,
    The help file is only officially supported document, but you
    can get that as a printable .pdf from

    http://LTspice.linear-tech.com/software/scad3.pdf

    Another good source of info is the independent users' group
    at http://groups.yahoo.com/group/LTspice

    --Mike
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-