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Converting square wave into buffered sine wave 45Mhz

user 1234
Prodigy 185 points

Hi, I have a square wave of max 45Mhz, high & low (3.3V & 0V), coming from output of a programmable oscillator.

Need to convert into equivalent frequency buffered pure sine wave? Is there any ready opamp circuit which can do this? 

I have seen this, but seems not buffered: http://www.learningaboutelectronics.com/Articles/Square-to-sine-wave-converter-circuit.php

  • 0
    Guru 140200 points

    Hi.

    this is usually done by the help of a passive 7-pole RLC-low pass filter. Have a look into the datasheets of chips providing DDS (direct digital synthesis). There you will find example circuits.

    Kai

  • 0 in reply to kai klaas69
    TI__Mastermind 30600 points
    A couple more docs that might be helpful:

    www.ti.com/.../sbfa003.pdf
    www.ti.com/.../snoa839.pdf

    Best,
    Paul
  • 0
    TI__Guru* 93105 points
    Hi User1234,

    Our Precision Op amps are not intended for use in a 45 MHz application due to their lower bandwidths. The application really calls for a high-order filter such as that recommended by Kai to remove the odd-order harmonic content contained in the square wave. At 45 MHz the inductor and capacitor values are low, and a physically small filter can be easily be constructed with surface mount inductors and capacitors.

    Once the square wave is filtered and reduced to a 45 MHz sine wave, the dc component can be removed by capacitively coupling the signal to the input of a high-speed op amp. TI has numerous High-Speed Op amps that can be configured to provide gain at 45 MHz. The folks on the High-Speed Amplifiers e2e forum can recommend the most suitable op amp for your application.

    Regards, Thomas
    Precision Amplifiers Applications Engineering