LM318 op amp, external compensation pins

Discussion in 'General Electronics Chat' started by patricktoday, Mar 23, 2013.

  1. patricktoday

    Thread Starter Member

    Feb 12, 2013
    157
    42
    I wish to use an LM318 as a comparator to generate a square wave from a sine wave signal. I am getting a measured rise time of about 300nS at 20kHz and about 600nS at 1kHz on my 'scope. Since the datasheet purports a typical slew rate of 70V/uS, I was expecting a rise time of about 129nS with a 9V swing.

    The chip has three compensation pins but I can't find hardly any info on them online. The datasheet states:
    Does anyone have an example of what "feed-forward" compensation is or how I could get a better rise time for this circuit?

    I have attached my circuit. (R2/C3 are meant to find the DC offset of the sine wave in case the sine wave's voltage shifts.)
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    Feedforward is typically where you use a capacitor across one of the feedback resistors which gives more feedback for fast moving AC signals.
     
  3. patricktoday

    Thread Starter Member

    Feb 12, 2013
    157
    42
    Well, that makes sense, but I'm pretty sure they're suggesting you can add some components to the internal compensation pins, but I don't really find any info on how this is supposed to be done.

     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    I read the data sheet and didn't see any info. I think it's an old part and the data sheet has been "minimized".
     
Loading...