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Urgent: reduce TTL 20MHz voltages...



Jan 1, 1970
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

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


Jan 1, 1970
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 :))