Differential Voltage Input in LTSpice

Discussion in 'Analog & Mixed-Signal Design' started by Leonardo Araya, Jul 15, 2017.

  1. Leonardo Araya

    Thread Starter New Member

    Jul 15, 2017
    2
    0
    Hi,
    I am developing an analog and digital circuit optimizer and I use LTSpice as a simulator. This tool gives you the value of Length and Width of the transistors that optimizes certain metrics, such as Gain, Power consumption, Transconductance, etc. So far the program has worked very well, but I am facing a problem with the simulation of a OTA, wich has a differential voltage input.

    The problem is that I do not know how to simulate a differential voltage input in Spice code. I am using this line, but I am not getting the expected values.

    .dc v+ 0 5 1m v- 0 -5 1m

    What I am trying to do is to change V+ from 0V to 5V and V- from 0V to -5V with a 1mV step; with the purpose of simulate a differential input, but it does not works.

    I hope you can help me.

    Regards
     
  2. ericgibbs

    Moderator

    Jan 29, 2010
    8,536
    1,713
    hi LA,
    I use this method, I usually have the voltage limits as +/-10mV into a bridge circuit.
    E
    EDIT:
    Alternate method. image 002
     
    Last edited: Jul 15, 2017
  3. Leonardo Araya

    Thread Starter New Member

    Jul 15, 2017
    2
    0
    Thanks for you answer. I'm going to try this method!

    Regards
     
  4. ericgibbs

    Moderator

    Jan 29, 2010
    8,536
    1,713
    hi LA,
    Relook at post #2 for DC option.
    Eric
     
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