Simulating a filter with LTSpice

Discussion in 'General Electronics Chat' started by atferrari, Apr 6, 2011.

  1. atferrari

    Thread Starter AAC Fanatic!

    Jan 6, 2004
    Last night I implemented an active 4 pole filter designed with Filterlab.

    It did not work as expected (my expectations could be wrong, I know :( ).

    I would like to simulate it. How to actually do the frequency sweeping in LTSpice?

    Whatever I try I get nothing or a message asking for "AC 1" to be present.

    Can anyone mention step by step how could I get there?

    PD: not that I want make simple things, difficult, but what if I have more than one AC signal source present?

    Gracias for any help.
    Last edited: Apr 6, 2011
  2. StayatHomeElectronics

    AAC Fanatic!

    Sep 25, 2008
    You need to make sure your voltage source has an AC component.

    If you put down a generic voltage source, you can edit the value by right clicking on it. The only boxes that are available to enter are the DC amplitude and series resistance, however, you should see an ADVANCED option button. Select ADVANCED and on the right side under the DC section is an AC small signal section. Add a "1" to the AC amplitude. I don't think you have to put anything under FUNCTION or DC analysis.

    Next to go EDIT -> Spice Analysis -> AC Analysis ... seems like you know where to go from here.

    I have not tried with multiple AC sources...

    Hope this helps.
  3. atferrari

    Thread Starter AAC Fanatic!

    Jan 6, 2004
    Oh, JUST THAT!! It was in front of me. :(

    Thanks for your time.