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Converter for sine wave to square wave at 0.5MHz

Fengqiang Li
Prodigy 20 points
Other Parts Discussed in Thread: LM311

I am looking for a converter which can translate a 8Vpp sinewave (-4V to 4V) into a 4Vpp square wave (0 to 4V) at 0.5MHz. The 0.5MHz, 8Vpp sinewave is from a function generator.

Can someone suggest a suitable chip (Schmitt trigger or comparator ) and a possible circuit layout to achieve this? The chips needs to be a DIP package and not a surface mount device.

  • 0
    TI__Guru 62935 points

    Hello Fengqiang,

    I think your circuit goals will be best achieved with a resistor network to scale the inputs into a comparator.

  • 0 in reply to Collin Wells
    Prodigy 20 points
    Hi Collin,

    Thank you very much for your quick reply. I really appreciate. I am totally new to the circuit design. Could you please give me some circuit layout to start with.

    Best,
    Fengqiang
  • 0
    TI__Guru 53876 points

    Hello Fengqiang,

    What power supply voltages do you have available? Is there a negative supply available? Will the 8Vpp be constant? Or could it vary in amplitude?

    What you are describing is commonly called "Zero Cross Detector" or "Data Slicer". A Google images search will show you some examples.

    The simplest way is to use a LM311 comparator which is designed for exactly this type of application. However, it will require at least +6V and -6V power supplies, and 500kHz may be running near it's speed limit. But it is available in DIP!

    If these supplies are not available, then the signal will need to be level-shifted above ground - either using some pull-up resistors and/or a AC coupling capacitor - to couple into a single supply comparator or even a logic gate. The 8Vpp can be attenuated down to something more easily handled by low-voltage comparators. This gets a little more complicated if we have to track a varying input level.

    Beware that your requirement for a DIP package will limit the available devices, as most of the high speed devices (<100ns) are in small packages.