Depletion-Mode FETs

And _what_ exactly is wrong with using a 12AX7? Parallel the two sections and there ya go! Need more power (and who doesn't)? There's always our old favorite, the 6L6.

I heard that someone in ?Russia? is still making 6L6/6550's ... I shudder to think what they must get for them.

Bob

Rad hard also. Harry

The heater needs 12V. Use a 2B7. If you parallel the two sides, you can get 20mA

I needed under an Ohm and 200V or so so it wasn't a problem finding a small enough one. I did have to taylor the rise on the gate so as not to drive the amplifiers into saturation with the gate capacitance, though.

Supertex makes some quite small ones.

Some of the newer ones have the advanage of a fast recovery on the body diode.

In article , Jim Thompson wrote: [...]

There are also some companies that sell them. I think his problem was that you can't find them in Digikey.

Well, I suppose that a metal plate with a hole punched in it is, technicaly, a "surface."

John

I read in sci.electronics.design that John Larkin wrote (in ) about 'Depletion-Mode FETs', on Wed, 23 Feb 2005:

If I had time, I'd point you to a source of *surface-mount* octal holders for the 6L6. B9A for the 12AX7 is admittedly more difficult.

That's "through-hole". This is a surface mount socket that could be used for a tube:

Best regards, Spehro Pefhany

P.S. does it bother anyone else that "octal bases" can have other than

Best regards, Spehro Pefhany

I read in sci.electronics.design that John Larkin wrote (in ) about 'Depletion-Mode FETs', on Thu, 24 Feb 2005:

Metal plate?? I meant a REAL surface mount holder, suitable for a plywood-baseboard-and-ebonite-panel equipment practice. The octal ones were made for relays (and you could get them with screw terminals to connect the wires), but I did see a piece of WW2 equipment that had UX-5 surface mount holders for a pair (or maybe four) 807s. Steel 'baseboard', though.

I read in sci.electronics.design that Spehro Pefhany wrote (in ) about 'Depletion-Mode FETs', on Thu, 24 Feb 2005:

That's the 11-contact 'sub-magnal' relay holder. More common than the octal version. But I don't know that there were any tubes that had the sub-magnal base.

I read in sci.electronics.design that Spehro Pefhany wrote (in ) about 'Depletion-Mode FETs', on Thu, 24 Feb 2005:

See my other article. All these contact arrangements have romantic names and/or alphanumeric codes.

Some of the early Tektronix scopes had a neat ceramic tube socket that had a sort of integral pillar with multiple solder lugs, all in one fused hunk. Passive parts could be hung here and there on the lugs. I'll take a pic tomorrow and post to abse. Their later scopes (545 era) used more conventional sockets, with the passive parts soldered between beautiful notched ceramic strips.

John

The old fashioned LED+optotransistor have soft transfer characteristics but the PhotoMOS switches I have looked at seem to have a knee...... nothing happens up to (say) 1mA of LED current, then everything happens in the next 0.1mA increase.