Simplest circuit for programmable pulse generator?

[sdc18]

Simplest circuit for pulse generator?

Need a circuit for generating a pulse of a desired width.

 

[betwixt]

What length of pulses are you thinking of?

An analog shift register based system would be horrendously complicated but if you can use digital parts and the pulse lengths aren't too short, the normal method would be to generate a clock at a specific frequency and count the cycles it produces. You can then start your pulse and reset the counter, wait for the count to reach your desired number and then stop your pulse. The pulse length is then (clock rate * number of counts you selected).

A small microprocessor would be the easiest solution but it would require a little coding.

Brian.

 

[sdc18]

Are there any simple ways for having better resolution than the clock period?

 

[KlausST]

Hi,

Where are your specifications?

Klaus

 

[FvM]

Are there any simple ways for having better resolution than the clock period?

You are posting in the Analog Circuit Design section, I won't expect a clock period in analog pulse generator.

 

[dick_freebird]

Among the things you need to declare are pulse repetition
rate min/max, pulse width min/max, what kind of timing
resources you will provide or expect to have provided to
your generator. Will you also want a programmable delay
(from some trigger event - do you want triggered or only
free running?)? Variable high, low levels / amplitude & offset
as well? All of these are "knobs" (actual, in my couple of
bench units; metaphorical, for a digital box).

What about jitter / stability? This alone might argue for a
more digital approach. You might like a 10MHz reference
(as is found on the back panel of spectrum analyzers,
if you are caring about phase noise you probably have
one) and a modern PLL +VCO (you could get >6MHz clock
this way) and then you "only" have to make the divider
logic work at speed.

The line driver output alone would be a challenge at
pulses below 10nS wide if you want large signal swings.

The bare minimum might be an astable multvibrator
clocking a monostable multivibrator (freq, width).
Switched-C or switched-R would make classic parts
"programable".

A FPGA might also be a way to go, although these
can be pretty "needy" and their eval kits, expensive.
But EVKs tend to have a lot of the resources you would
need (reference clock, USB interface). The output swing
would be limited, and you might need something extra
for that.

You should draw the lines before you start trying to color.

You should look at eBay and Amazon if you need the tool
more than the experience of creating it (or trying). I have
found pretty cheap arbs and pulse gens with USB interfaces.
At prices which make "make vs buy" a no-brainer.

 

[D.A.(Tony)Stewart]

The common methods I have used include ECL XOR gates with cap current delay in sub-nanosecond range or CMOS for sub-microsecond range but symmetry for CMOS depends on family.

Asymmetry is greater in CMOS than CML and ECL for rising and falling edge so delay times and supplier tolerances are a factor.

I suggest 74ALC 25 Ohm is +/-25% and 74HC is 50 Ohm +/-25% approx. using RC delay on XOR input comparing input and delayed input.. But you can verify.

I think in general CML is best target for a solution.


What's up with the newbie type question with no specs?