Re: 067-0513-00 Pulse Generator


What is needed to get rise times faster than 100 picoseconds with an
avalanche pulse generator?

Is all surface mount construction sufficient? I suspect the lead
inductance is the major limitation. A transistor with dual leads on
the collector and emitter would be handy for this.

I am not impressed with the aberrations of the avalanche pulse
generator design at the silionvalleygarage link. If I went this
route, I would try adding a diode disconnect circuit which is common
in flat level pulse generators.

On Wed, 21 Oct 2015 13:31:18 -0700, you wrote:

Hi Roger,
As you point out avalanche transistor pulsers are incredibly simple to
build. Almost any transistor will work, and a short piece of coax is all you
need to stretch the pulse. Plus they generate a lot of voltage (unlike TDs)
which in some cases is a plus. Early in my career I built one and was really
impressed at the results.

If you are very careful you can get rise times under 30pSec. But generally
speaking it takes a good sampler to be able to measure those kinds of edge
speeds. Somewhere about a year ago on the internet I came across somebody
that published the test results of the avalanche speeds he measured of about
15 0r 20 transistors. They were all pretty fast but some were incredible. I
wish I could remember where I saw that list.

Dennis Tillman W7PF

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