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Urgent: reduce TTL 20MHz voltages...

Discussion in 'Electronic Basics' started by Ale, Mar 1, 2005.

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  1. Ale

    Ale Guest

    Hi.... I have a stupid question... and I have to solve it as soon as
    possible... but this, probably, does not matter :)

    Well, the problem is trivial, but I did not solve it.

    I have a 20MHz TTL. I have a PA that will drive a LED. All work when I use a
    variable signal generator, but when I use the TTL source, I know I have to
    attenuate the TTL signal because the PA accept a maximum of 200mVpp. I
    assumed to solve the problem in this manner:

    IN -----\/\/\/\------ GND
    | OUT

    Well.... I put also in series of the IN and the resistor a 75Ohm resostor to
    avoid shortcut.

    OK.... so many years I do not make any electronics that I am not following
    the point.... As out I have a distorted signal. Fair enough, but I could
    leave with a smoothing, what I get is a multi-step "square-wave".
    Furthermore I do not have a real control of the levels, but I just get all
    or none effect with a 1K3 and 100K variable resistors....

    How can I solve this trivial problem.... in a simple a fast way?... thanks
  2. Ale

    Ale Guest

    Please almost ignore my previous message!!!!!
    I only had a problem with the impedence of the oscilloscope... now it is
    ok.... (I hope also with the PA :))
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