HF pulse generator

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Hi all,

  I'm looking to create a high simple high frequency (10Mhz) pulse with a
low component count.  Anyone know of some simple HF one-shot pulse circuits
that require a small number of parts. For example, every time a
microcontroller clocks a line, a quick pulse would be seen on the output.
This is too high frequency for a 555, and I would like to stay away from
inductors for potential production purposes, but I'm sure there's a handy
single BJT circuit out there.  any ideas?  :o)

Thanks in advance for your help.

Best Regards,
  Adam Kumpf



Re: HF pulse generator
Hello Adam,

You could use a fast Schmitt trigger wired up as a differentiator. If
not familiar with that look at figure 7 on the ON Semi data sheet for
the MC14106B. But pick a faster chip for this application, maybe from
the 74HC series. If the uC runs at less than 5V look at Schmitt tiggers
in one of the fast low voltage logic series from TI. In case you'd
rather take a NAND because you need some of these elsewhere, most series
also offer quad NAND chips with Schmitt inputs.

Besides that one Schmitt gate you only need a resistor and a capacitor,
no inductor. It doesn't get much cheaper than that.

Whatever you do, keep in mind the pulse repetion rate and whether there
is any chance that the series cap might drive into the input diodes.
That could be a concern, especially if the uC ports are a bit weak. Or
too strong to cause latch-up.

Regards, Joerg

http://www.analogconsultants.com

Re: HF pulse generator
Quoted text here. Click to load it

Are you worrying about repetition rate or pulse length?  There are
at least a million options, from analog one-shots through clocked
logic.  I suspect I would lean towards a clocked PLA which can be
very cheap, accurate, and flexible.

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