Fet switch spikes.

[George Herold]

On Friday, June 12, 2015 at 5:05:04 PM UTC-4, M Philbrook wrote:

In article <c694f567-d00f-4a36-88f7-0898ee7e93ef@googlegroups.com>,
gherold@teachspin.com says...

On Thursday, June 11, 2015 at 5:49:01 PM UTC-4, John Fields wrote:
On Mon, 8 Jun 2015 19:17:56 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:


Can I switch a relay at ~1 kHz?
(I guess I only need a good edge..
to measure the frequency response.)

George H.

A mercury wetted reed relay will give you edges out to substantially
less than 100 picoseconds, but the ones I have (Fujitsu
FMR-824D06/1A) will only switch up to about 100 Hz.

If that'll work for you, email me a physical address I can send one
to and it's yours.

John Fields

Hi John, Gee, thanks for the offer. The little jeft looks to be fine.
And though I can look at the response from an edge and figure out the
BW, it will be harder for the grad. student I'm helping.
The easiest will be if we change the frequency of the square wave
and measure the response up top. (of the probe)

I know this may sound strange to you, but during testing last
week I got the impression that he was a little surprised to find
the frequency that we wiggled at the bottom was the same frequency
that was measured at the top. He wanted to check a few times, look
at frequency on generator, measure frequency with 'scope.... and
then of course the 'scope doens't always measure the right frequency.

George H.


How's that? I've always had good luck with my scopes reporting
correct frequencys?

Oh the signal was noisy. (pick-up mostly.)
The scope doesn't know which zero crossing to look at.

George H.

I can understand maybe an analog not being rite on but even my
Tek 350Mhz analog, seems to be good with in reason.

I mean I wouldn't use it as a precise indicator..

Jamie