J308 for really-low voltage oscillator

No, on a trapezoid! ;-)

...

And they're the same transistor? :)

Wow, a lot of info there!

Thanks!

Michael

Thanks for the info, John.

That family of drain curves (DSC01311.JPG) shows the Early voltage problem very well. The -0.3V curve in the 3508 datasheet (P 3) passes through (3.5V, 23 mA) and (1.2V, 10 mA) for an Early voltage of

VA = - (10 mA/13 mA)*(3.5 V - 1.2 V) -1.2 V = 0.6 V.

OTOH the saturation plot (DSC01309.JPG) shows the nice high transconductance, like 300 mA/V at 1V D-S.

The Murata BLM18BB-series beads do a nice job of stabilizing a BFP640 cascode device, though the bandwidth sacrifice is considerable. One fine day I'll have to get down Carson and Hollister and figure out a broader-bandwidth solution, but so far it's been fast enough just with the bead.

Cheers

Phil Hobbs

Since I generally slam them on or off, Early voltage isn't a problem.

They do enhance nicely, to around 2x Idss.

Oscillation isn't a problem either!

I bet a BFP640 could get in a cycle or two even with your edge rates. ;)

Cheers

Phil Hobbs

There's an idea too!

Still, I'd likely need to increase the voltage to something more than 1 volt.

Also, strange things can happen when I string lots of weak batteries together... sometimes I noticed a battery reversing polarity when stringing together 8 NiMH cells in series :o

Thanks,

Michael

Not at all unexpected. The big battery users (diesel/electric submarines, for example) always had to do cell-by-cell testing, and shunting a dead or weak cell was a routine maintenance chore (unless it related to battle damage...).