Fast logic parts for my digital oscilloscope

Discussion in 'General Electronics Chat' started by CVMichael, Jun 28, 2010.

  1. CVMichael

    Thread Starter Senior Member

    Aug 3, 2007
    I have a 500 MHz Logic Analyzer, that has the option to display analog data also. I created a test board using an AD9059 to convert from analog to digital at 60MSPS and everything works well. AD9059 is a double ADC, so I can measure 2 analog inputs at the same time.

    But there are a few improvements/additions that I want to add, but it's a hell finding parts that are fast enough.

    First of all I want an 8 bit optocoupler that can go up to 60MHz (it would be even better if it would go up to 500MHz)
    Why do I want that ? because I want to separate the ground of the ADC converter with the logic analyzer, this way I am not limited to what I want to measure.

    Second, I need some kind of logical switch to select what analog I want to use, and when I don't use the analog, to "pass through" all the 8 bits (ports). I think this can be accomplished with 2 AND gates, and one OR gate. And I need the "switch" (logical gates) to work at 500 MHz, since the logic analyzer works at that speed.
    I attached a picture with the logical switch that I want to use.

    I also attached a diagram with what I want to accomplish. Each line is actually 8 bits (8 ports).
  2. Markd77

    Senior Member

    Sep 7, 2009
    I was thinking, if you power down the AD, assuming the outputs would be zero and could safely tolerate logic input from the rest, that would simplify things.
    Maybe you could find a buffer for the digital that could be powered down too.
  3. CVMichael

    Thread Starter Senior Member

    Aug 3, 2007
    So, there are systems that work at hundreds of gigabits per second (fibre optics for example), but there are no logic gates or optocouplers that can go as fast as a measley 500MHz ?

    A "fibre" (from fibre optics) is basically an optocoupler isn't it ?

    Are all these parts hidden for the general public ?