Transistor selection (ii)

You might try looking for CRT driver transistors.

Sanyo's 2sc4188seems to meet your requirements: Vcbo=200V Ic = 100mA Pc = 10W Ft=150MHz

HTH, James Arthur

Yep, I was just about to post the same. Often it is cheaper and more practical to take a few video transistors in parallel instead of one expensive boutique version. They are really cheap. The BF series contains some as well.

Don't know how YOU would go about that but I'd look in my "secret" references and come up with

The "answer" is an old set of data books. Back in the heyday of discrete transistors it was a subscription service. They no longer seem to exist and even a Google search turned up nothing. They were called D.A.T.A. Inc. And had volumes for Transisor, diodes, SCRs and many other things. The one I have is from 1978 so they aren't too up to date put often you can cross-reference to more modern parts.

Someone REALLY needs to put the last version of those old books on the internet!

MCM is taking orders (for later delivery) for "subs" for Sanyo's 2SC4188 (200V 10W 150MHz) and for Toshiba's 2sc2238b (200V 25W 100MHz), and 2sc1569 (300V 12.5W 100MHz), and for Matsushita - Panasonic's 2sc1819 (300V 15W 100MHz).

Toshiba's 2sc2238 (160V 25W 100MHz) is in stock.

We have quite a few extremely hard to find 2SC and similar ic's in stock at

Prices are far below anywhere else.

Tim Williams snipped-for-privacy@charter.net posted to sci.electronics.design:

Along the way the changes in o'scope CRT deflection went from simple parallel plates to distributed deflection. This added quite a bit to the capacitance but improved the deflection sensitivity from many (tens of) volts per inch to (many tens of) millivolts per inch. This reduced the required magnitude of deflection voltage to fast transistor range. Trying to speed up a HV deflection amplifier without resorting to ultrafast HV FET's may be impractical.

Reminds me, I think I read in my Tek475's manual something about multiple deflection. The CRT has a number of pins along it.

And that leads to another question ;-) -- would there be any value in MOSFETs for this? Probably cascoded, so the biasing is still handled by a nice and fast transistor. RLC of the gate is the ultimate roadblock, isn't it? Could still be pushed harder with excessive drive current, which I don't really have much of a problem with, as I have a few fast, ampy transistors on hand.

If you meant JFETs, where do you find JFETs at more than 30V, 10mA and TO-18 / TO-92 / etc., anyway? JFETs are so unpopular, it's not fair! (Checking Digikey, I see no more than 55V or 50mA -- 500mA is mentioned but it's got to be a Fairchild typo.)

Tim

-- Deep Fryer: A very philosophical monk. Website @

I don't know in particular, but check Interfet. High I is hard to come by in a JFET (among other things).

greater than 100V, but low I:

Tim Williams snipped-for-privacy@charter.net posted to sci.electronics.design:

I suspect that would be a tradeoff, complexity versus cost.

Then, no. Now yes. Some of the specs for wideband and SHF mosfets today are spectacular compared Tek 475 vintage.

Nothing wrong with that. Just remember that as speed continues to increase, volts as well as volts/naonsecond matter to handle L issues in a small fractions of an inch.

Unpopular? They are very useful and popular in tuners and UHF/SHF/EHF front ends, just not so much elsewhere anymore.

No, not so hard. You find these by looking for low Ron JFETs, which happen to also have very high Idss. An example is the J105, with Rds < 3 ohms and Idss = 500mA. It's available in TO-92, sot-223 (JFTJ105) packages.

But note, for linear use one wouldn't be likely to use a possible-high operating current, like 500mA, unless Vds was awkwardly low, because the die would overheat. However we certainly do use large-die JFETs in linear appliations, namely low-noise amplifiers, because they have very low e_n. Then we set Id = 5mA or 10mA, etc.

I:

Also try:

The J108 or SST108 has a high IDSS.