Waveform Generator Problem

Discussion in 'Homework Help' started by callum2510, Sep 7, 2015.

  1. callum2510

    Thread Starter New Member

    Aug 26, 2015
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    Hi, Just looking for some verification if I have complete this correctly? I'm not 100% sure on my solution. Screen Shot 2015-08-28 at 10.31.32 am.png media-867-867f15cc-b9a9-4289-9e3c-425f15e5222b-phpSTCI5Y.png
     
  2. WBahn

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    Mar 31, 2012
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    It is incorrect to say that the inputs of the first opamp are at virtual ground. The term "virtual ground" means that the voltage is 0V (i.e., the same voltage as your "ground") even though that node isn't connected to ground. That is not the case here. These two nodes can be at a voltage other than 0V, but they have to be at the same voltage even though they are not connected to each other. This is known as a "virtual short". The distinction is important.
     
  3. shteii01

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    Feb 19, 2010
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  4. shteii01

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    I got C1=0.1 uF.
     
  5. callum2510

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    Aug 26, 2015
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    Do you mind me asking how you got that?
     
  6. MikeML

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    That is not correct either. The first opamp is acting as a multivibrator, so the inputs are almost never at the same voltage...

    271.gif
     
    Last edited: Sep 7, 2015
  7. shteii01

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    <br />
f=\frac{1}{T}<br />
T=\frac{1}{f}<br />
f=82 Hz<br />
    Find T.


    T is known.
    R3 is known.
    Find B.
    Plug everything in and solve for C1.
    <br />
T=2*tau*ln(\frac{1+B}{1-B})<br />
tau=R_{3}*C_{1}<br />
B=\frac{R_{1}}{R_{1}+R_{2}}<br />
     
    Last edited: Sep 10, 2015
    callum2510 likes this.
  8. crutschow

    Expert

    Mar 14, 2008
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    That's true if the op amp is operating in the linear mode but here it's operating as a comparator in a square-wave relaxation oscillator circuit, so the two inputs are only at the same voltage at the instant the output changes state.

    Edit: Okay, Mike beat me to it. ;)
     
  9. WBahn

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    Hello! Homework HELP!
     
  10. WBahn

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    True. I didn't consider the circuit beyond seeing the notation -- only had a few seconds to make a reply when I got called away.
     
  11. WBahn

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    Wouldn't it be even more helpful if you wrote up the entire solution and submitted it for the TS?
     
  12. shteii01

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    The dude is too clueless. Me solving this one little problem is not going to make him finish that class with an A. I will be very surprised if the dude can get a B for this class. My bet is on C or D.
     
  13. callum2510

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    Aug 26, 2015
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    Last edited: Sep 9, 2015
  14. callum2510

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    Aug 26, 2015
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    I wasn't looking for a answer more an explanation. Why have a homework help section on the forum if you ***** are going to criticize me asking for some help?!
     
    Last edited by a moderator: Sep 9, 2015
  15. callum2510

    Thread Starter New Member

    Aug 26, 2015
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    How the **** would you know what my academics capabilities are? Yes some questions are challenging for others hence why I approached this forum for clarification. You're just an old American wanker that loves to assume stuff without any knowledge
     
    Last edited by a moderator: Sep 9, 2015
  16. WBahn

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    Watch the language -- that will get you banned pretty quickly.

    I wasn't criticizing you at all -- I was making remarks aims at shteii01 (i.e., the person whose post I was responding to).
     
  17. WBahn

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    The you are always free to go elsewhere. But obscene language won't be tolerated here.
     
  18. JoeJester

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    You thanked shteii01 and then quoted his post with no other comments.

    Then you went on a rant.

    Is there a question forthcoming?
     
  19. shteii01

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    Look. I was responding to WBahn.

    Generally speaking, I was rude to callum2510. I admit it. So his response does not surprise me. However! I was rude. He was rude. I got what I deserved. The original question/homework problem was answered. Lock this thread and let us all move on.
     
  20. JoeJester

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    Generally threads are not locked.

    It really doesn't matter who you responded to. In your second rant, you mentioned shteii01. I personally thought it was uncalled for, so I decided to ask if there was more questions. Since there's not, my time in this thread is done.
     
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