RF Transistor Noise Source

...where is that goat?

• Have never fiddled with Trr, stored charge, etc so cannot comment usefully. 7mA is usually in the stable region, so ASSuMEing a sine drive, the diode could be in its stable region for up to maybe half of the reverse swing.

ut

ar

ome

st

ck

n is a

ge.

hort time.

now

hen

arts in

eet

sed

Hello Robert (and others),

During the reverse recovery/breakdown measurements with the 1N4448 array, there were some non-repetitive phenomena. I further investigated this with a current limited source with good RF decoupling (100nA) and 150 Ohms impedance.

Amazing results. Above about 20uA average reverse current, current spikes do occur due to instability. The measured rise/fall times are very likely less then 2.5ns (limited by my test setup). Peak current is 40mA (20uA average), with a lower longer lasting tail current. Even up to 8mA (that is 1W dissipation into a 1N4448), the instability remains, until it becomes stable due to self-heating. Peak current did not increase with increasing average current, but tail becomes longer and average PRF increases.

When only self-heating is taken into account, 1.3mA reverse current (200mW diode dissipation) becomes stable after a while due to self- heating. When externally heating the diode (I guess to about 80 degrees), all instability disappears (also at lower currents).

So without external heating, 1N4448 is not a good noise source.

Best regards and a successful 2010,

Wim PA3DJS

What do you recommend for a tornado?

Windbreaker.

A bunker.

Cheers

Phil Hobbs

How do you wear a Bunker?

Ask Edith.

Probably better than Gloria. Have you seen her lately?

Good line. Just re-watching "All in the Family" AND "MASH" ;-) ...Jim Thompson

BABE! ...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

The later years of MASH when Alan Alda began writing and directing are probably a skosh too liberal for your tastes? :-)

If a tornado is coming your way, you'll figure it out.

Cheers

Phil Hobbs

...ask "Archie"???

Not for a long time. :(

No, that's what a tornado shelter is for. Underground.

I didn't need that :-( I prefer to remember her from the TV series. ...Jim Thompson

Funny. When MASH was first on TV I was too busy raising 4 children to watch much TV, and, in addition, didn't really like the show.

Now I find it both hilarious and sad.

BTW: There's a BIG difference between "liberal" and "leftist weenie".

Remember my political "score"... almost fully into the Libertarian corner. ...Jim Thompson

Hi Jim,

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

OK. Who (of well-known individuals) would you consider pretty liberal but not a leftist weenie? ;-)

---Joel