Op-amp Schematic

Discussion in 'Homework Help' started by kiwi101, Apr 23, 2015.

  1. kiwi101

    Thread Starter Member

    Feb 18, 2014
    Hey guys,

    I'm trying to make a triangle wave generator circuit on cadence but in order to do that I have to make an OP-AMP first. This is the schematic I made for the OP-AMP and when I plot the Vout vs t or Vin vs t, it's clear to see that something is off.
    Any suggestions are appreciated.
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    I suspect that this should have been posted in Homework

    What is the voltage gain of the opamp circuit supposed to be? What is it the way you have it connected? Inverting or non-inverting?

    Ask your self, what is the input impedance at the inverting input? What is the input bias current to the opamp inputs? What is the voltage across R0?
  3. WBahn


    Mar 31, 2012
    MOD NOTE: Moved from The Projects Forum to Homework Help.
  4. WBahn


    Mar 31, 2012
    Your plot only has one trace. Is it Vout, Vin, or Vpluto?

    Have you bothered to LOOK at your circuit (middle attachment) to see if it makes any sense?

    It's hard to tell if your output (assuming it were labeled for us non-crystal ball users) is what should be expected since you don't bother indicating what the circuit is SUPPOSED to do.

    We are NOT mind readers!
  5. WBahn


    Mar 31, 2012
    Or even more basic, how is the output supposed to influence the opamp in any way given how the feedback resistor is connected?
  6. kdillinger

    Active Member

    Jul 26, 2009
    It's a shame there is not a free version of Virtuoso somewhere. I am presuming everything is ok with your differential pair, current source, and tail current. Conceptually, your op-amp works.
    One pertinent issue is that your feedback is not correct. R1 should be connected from Vout to Vin-. Else you are making a weird feedback factor.