triangular to sine wave

Discussion in 'The Projects Forum' started by kahafeez, Dec 15, 2008.

  1. kahafeez

    Thread Starter Active Member

    Dec 2, 2008
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    hi people i constructed a 741 op amp oscillator. it is giving an output bt its a triangular wave.... but i want a pure sine wave... how do i get a sine wave... the freq is around 40KHz.... i used a wein bridge config... like the one shown in the figure..... either tell me how to get a sine from the osc or tell me how to shape a triangular to a sine wave.....
     
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  2. Wendy

    Moderator

    Mar 24, 2008
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    One of your capacitors is shorted, this would contribute. You will probably need a better op amp, but fix that cap first.
     
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    If you do it right, that is a Wien Bridge oscillator. It generates sine waves. Google "Wien Bridge" for lots of information.
     
  4. Audioguru

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    Dec 20, 2007
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    The lousy old 741 opamp (it is 40 years old this year) is so slow that it turns all signals above only 9khz into a triangle-wave. A TL071 audio opamp and many other opamps work up to 100kHz. An OP134 audio opamp work up to 250kHz.
     
  5. Ron H

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    AG, you should add parenthetically: "This is a recording.";)
     
  6. Audioguru

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    Why do teachers insist that their students use lousy old opamps?
    Why do teachers even talk about lousy old opamps?
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    When you were learning to drive, did you start off in a Lamborghini Countach?

    Probably not...

    I started off driving in a '63 Fiat 1100D (looked like a scaled-down Checker cab, engine was a 1088CC 4-cylinder) that had tires thin as baloney skins in the rear. It was so underpowered, you'd have to drive it off a cliff with a tailwind to get it up to 70mph.

    It sure made me appreciate my '65 Mustang GT convertible a lot more. ;)
     
  8. kahafeez

    Thread Starter Active Member

    Dec 2, 2008
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    thanks people. i'll use TL071. the cap is shorted in this schematic. on the breadboard it was ok.
     
  9. leftyretro

    Active Member

    Nov 25, 2008
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    Hey! I had a brand new '66 Mustang GT fastback, yellow with black interior. I loved that car, but sold it when married and the kids started popping out.

    PS: I found an interesting backdoor circuit in that car. Without a key in the ignition if you turned on the safety blinker, put foot on brake the radio would pulsate on and off with the blinker timing :D
    Lefty
     
  10. Ron H

    AAC Fanatic!

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    So what's the lesson here? Start out with a crappy op amp, so you will appreciate the better ones when you can afford them?:D
     
  11. Ron H

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    Man! That could be really handy!;)
     
  12. Audioguru

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    Dec 20, 2007
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    I think that teachers don't know that a lousy old 741 opamp has poor performance and that there are much better opamps available at the almost the same price. Besides, the text books are old.

    Today at Digikey, an LM741 single opamp costs $.49US each, A much better single TL071 costs $.53US each and a much better dual TL072 costs $.50US each.
     
  13. Wendy

    Moderator

    Mar 24, 2008
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    Don't worry, students are killing them one at a time, then they get the good ones.

    I remember seeing the top pop off one in one of my classes so long ago.
     
  14. Audioguru

    New Member

    Dec 20, 2007
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    The teachers? Hee, hee.
     
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