Re: breadboarding fast, tiny stuff

On Sat, 01 Mar 2008 18:58:28 GMT, JosephKK <quiettechblue@xxxxxxxxx>
wrote:

John Larkin wrote:
We got some samples of an NEC hj fet and were wondering what its
time-domain response might be like. The part is only 2x2 mm and the
leads are 1.2 mm pitch, and I hadn't previously had a lot of luck
breadboarding stuff like this.

We found two tricks:

Get a piece of copperclad, epoxy-glass or preferably teflon; the
teflon is easier to cut. Cut out "pads" with a very sharp xacto knife,
under a Mantis magnifier. This will make horrible burrs and shorts, so
the first trick is to scrub it really hard with a Scotchbrite pad
between cuts. This cleans it up beautifully.

The second trick is to use small patches of kapton tape as insulators.
like where parts join or whatever. Soldering doesn't bother it at all.

ftp://66.117.156.8/FetTest.zip

Here, the fet is in a first-pass test circuit, just to see how fast we
can turn it on and off. The TDR pulse from the sampling head is the
gate drive, 0 (Idss) to -0.5 (pretty much off) at 50 ohms source z.

The drain is pulled up through a 47 ohm resistor, and the 150 ohm
resistor off to the side is an "attenuator" into the other scope
channel. The turnon fall is very clean, no nasty ringing or whatever,
with a 190 ps fall time. Turnoff is similar; these things don't store
charge! The TDR of the gate (lower trace) indicates that the gate
capacitance is loading the drive, so we need a bigger gate swing, from
a lower source impedance, to make this thing switch really fast. That
will be next.

John


Hell, you have a webpage to work with post gif's not zip's.


I'm offering free data and advice, and you're whining about the price.

And it's not a web page, it's an FTP site.

And my camera makes jpeg's, not gif's.


Did I leave anything out?

John

.

Relevant Pages

  • Re: breadboarding fast, tiny stuff
    ... The drain is pulled up through a 47 ohm resistor, ... The turnon fall is very clean, no nasty ringing or whatever, ... The TDR of the gate indicates that the gate ... a lower source impedance, to make this thing switch really fast. ...
    (sci.electronics.design)
  • Re: breadboarding fast, tiny stuff
    ... The drain is pulled up through a 47 ohm resistor, ... The turnon fall is very clean, no nasty ringing or whatever, ... The TDR of the gate indicates that the gate ... a lower source impedance, to make this thing switch really fast. ...
    (sci.electronics.design)
  • Re: breadboarding fast, tiny stuff
    ... The drain is pulled up through a 47 ohm resistor, ... The turnon fall is very clean, no nasty ringing or whatever, ... The TDR of the gate indicates that the gate ... a lower source impedance, to make this thing switch really fast. ...
    (sci.electronics.design)
  • Re: breadboarding fast, tiny stuff
    ... The turnon fall is very clean, no nasty ringing or whatever, ... The TDR of the gate indicates that the gate ... a lower source impedance, to make this thing switch really fast. ... You can't unzip files? ...
    (sci.electronics.design)
  • Re: breadboarding fast, tiny stuff
    ... The turnon fall is very clean, no nasty ringing or whatever, ... The TDR of the gate indicates that the gate ... a lower source impedance, to make this thing switch really fast. ... I'm offering free data and advice, and you're whining about the price. ...
    (sci.electronics.design)
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