opamp help

Discussion in 'General Electronics Chat' started by Xufyan, Sep 10, 2011.

  1. Xufyan

    Thread Starter Member

    Aug 3, 2010
    114
    0
    is it possible to design an opamp circuit that take the sin of input signal,
    ie,

    Vo = Sin(Vi) ??
     
  2. tgotwalt1158

    Member

    Feb 28, 2011
    111
    18
    The attached circuit implements the mathematical relationship between the sine and cosine trigonometric functions. Mathematically, if you integrate a sine wave, you get an inverted cosine wave. Basically, it's the same waveform but shifted 90° in phase. Then, if you integrate that cosine wave, you get another 90° phase shift, producing a negative sine wave. Of course, each op amp integrator introduces an inversion as well, so the output of the first integrator is actually a non-inverted cosine wave. This is reversed again by the second integrator, so its output is still a negative sine wave. All we have to do is invert that negative sine wave to get our original sine wave back again. The attached circuit accomplishes this.
     
  3. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
    47
    more or less right but not an answer to the question.
     
  4. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
    47
    For what range of v in? For what rate of change? You can use sin x aprox x for small x. Then using diodes you can insert some break points to improve the aprox. This approach runs into serious problems for x > pi/2. Try looking up piece wise linear circuits. If this does not work consider a microcontroller.
     
  5. JMac3108

    Active Member

    Aug 16, 2010
    349
    66
    Do you really need a circut that ouptus the sine of an arbitrary input signal? If you have a particular type of input signal in your application, it will be easier to come up wth a circuit to take the sine of it.
     
  6. Xufyan

    Thread Starter Member

    Aug 3, 2010
    114
    0
    the AC side is far so easy , integrating a square wave twice gives a sine wave and integrating triangle waves output sine wave but what if i apply Dc voltage at the input side of Opamp ? how it will generate sin output ?
    like if the input is 0.5volts the output must be sin(0.5)

    is there any way to convert dc voltage to Square wave ? so that i can then convertit into sin wave ??
     
    Last edited: Sep 11, 2011
  7. tgotwalt1158

    Member

    Feb 28, 2011
    111
    18
    Here are some Sine Functions and their graphs. If you could produce equivalent op-amp circuit, you will achieve your goal.
    See the attached files
     
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