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Relaxation Oscillator Multisim

  1. Mar 4, 2014 #1

    Maylis

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    Gold Member

    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    I am doing page 4 of the lab attached, and I am trying to simulate the relaxation oscillator in Figure 2. However, I am not getting a square wave like the lab suggests I should get. I have been able to do the derivation at the bottom of the page.

    I have attached my multisim diagram as well as my transient analysis of the probe at the output of the op-amp. What is going on here??

    Based on my calculation of the period T, using R=1000 Ω and C = 100 μF, I get a period of .220 seconds, and here the spacing between the ''squares'' (which are not very squarey) is slightly under 4 seconds. It also goes above my rail of 5 V.

    I'm also stuck on the derivation on page 6,

    Vout = -∫Vin/RC dt and proving that it outputs a triangle wave from a square wave.
     

    Attached Files:

    Last edited: Mar 5, 2014
  2. jcsd
  3. Mar 5, 2014 #2

    Maylis

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    Gold Member

    I have figured out that part about the relaxation oscillator, and my multisim now works. I am on the part about the triangle wave generator (page 7). I have derived the relationship, and now I am stuck making my triangle wave output.

    I just took the circuit from the previous slide as my square wave and attached it to the triangle generator, and the oscillator just won't read a triangle.

    The question asks to pick values of R and C such that the triangle waveform will have an amplitude of 4 V. I am a bit confused about this part I believe.

    I just said that the y-axis is 4, and since f=10, then the time, or x-axis, is 0.1. That means RC = 40. So C = 40/R. Choose R=1000, then C = .04 F.

    The supply is 5 V from my relaxation oscillator, so my square wave should be +/- 5V, but the oscilloscope for my triangle generator gives me nothing.
     

    Attached Files:

    Last edited: Mar 5, 2014
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