Sawtooth signal not being amplified by opamp as much?

Discussion in 'General Electronics Chat' started by zero_coke, Nov 14, 2012.

  1. zero_coke

    Thread Starter Active Member

    Apr 22, 2009
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    When I simulated a function generator connected to a basic non-inverting setup with R2/R1 = 2, and my function generator was outputting 4Vpk, I was not getting 8Vpk at the output of the non-inverting opamp. I was getting something like 6.9Vpk. When I switched to sine wave I got 8.5Vpk (Opamp was NE5532). Why is this happening?
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    What is the Vcc on the op-amp?
    Does the datasheet say that the output will go all the way to the rail?

    Depending on the output stage the output is being limited by the internal circuitry. Near the rails it deviates from ideal linear behavior. That is what is happening. Are you surprised? Why?
     
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Post a schematic.
    BTW, a noninverting op amp has a gain of 1+R2/R1, which in your case is 3.
     
  4. crutschow

    Expert

    Mar 14, 2008
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    What is the signal frequency?
     
  5. zero_coke

    Thread Starter Active Member

    Apr 22, 2009
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    Papabravo: I was using a Vcc/Vdd of +/- 10V and the opamp was the NE5532AP. The input was a 4Vpk AC signal or 8Vp-p.

    Ron: I'm sorry, yes, the gain should be 1+R2/R1 for a non-inverting setup.

    Crutschow: Signal frequency was 1Khz

    I changed my R2/R1 to be 1 so then I get a gain of 2 in total.

    This worked, I was just misinterpreting it. Sorry guys. For the sinusoidal waveform, now I get an output of 16Vp-p and an RMS output of 5.65V (8/root(2)). For the sawtooth, I get an output of 16Vp-p but now an RMS output of 4.62V (8/root(3)).
     
    Last edited: Nov 14, 2012
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