why not just get a LM555 timer IC and generate a 10KHz pulse for your
project, that output signal should not disappear.



wrote in message
oups.com...
I'm trying to help my son with his electronics lab work for school. The
project is to set up an exclusive or gate, an SN or DM 7486 and apply a
1.0KHZ square wave at a TTL level, (which I'm assuming is simply
5.0Vpp) to one input while alternating an either high or low level to
the other input. We are to observe the output of the gate on the scope
and then draw up a waveform display depicting the output corresponding
to the different inputs applied.
I'm using an old Systron Donner Datapulse 101 pulse generator which has
two outputs available: a positive and a negative. They are marked
"output into 50 ohms" I set up a 5.0Vpp 1.0ms positive going pulse with
a 50% duty cycle as measured on the scope and then attempted to apply
it to the input of the gate. As soon as I did this though the pulse
disappeared as though the gate's input was loading it down. I next
placed a 50 ohm termination on the output and tried it again. I noted
that the output (before I connecteed it to the gate had decreased
slightly due to the additional loading the 50 ohms provided, so I
boosted it back up to the 5.0V level and observed that the pulse once
again disappeared a soon as I connected it to the gate input. I am
aware that some generators have a "TTL" output. I suppose that I should
know this but its been a long time since I've played around with any
TTL stuff so I have to ask:
a. Is my 5.0V pp signal level correct?
b. Would a generator having a "TTL" output provide a higher current
drive signal into the gate? And is this what is needed?
c. Is this why my generator is being loaded (I suspect) down?
d. Can I do anything about this short of trying to find another
generator?
(Which would be difficult, if in fact it appears that this is the
problem).
The project is due on Thursday so any assistance anyone may be able to
offer would be most sincerely appreciated.
Lenny Stein, Barlen Electronics