10% thru-hole air or phenolic inductors?

But watch the resin, it can disintegrate over time.

I prefer it to be reflected back. Done it before, saves a lot over energy and most of all, heat.

Ok, ok, but I was still a youngster. There was the choice between buying a 2nd T200 core which would have set me back $15 with shipping, or a crate of Koenig Pilsener beer for around $10 plus deposit. The crate won ...

Or you can burn the paint off. I've done that.

I used to have a minigrabber with a ferrite bead melted into it, from an amp that needed two beads to stabilize it, and only had one. It got thrown out in some move.

Cheers

Phil Hobbs

Until the move to the US I had shrapnel fragments from a large ceramic capacitor. As a kid I thought those are invincible, have no ESR to speak of and all that ... PHOOOMP ... it blew its guts out the side of the amplifier and turned itself into bubbly green glass within milliseconds.

The wall (European style plaster) looked like it had been hit with buckshot.

Or both. I've done that with about 50W of near 1MHz:

Tim

I'm going to be doing more of that, as I move into higher frequency switching circuits... Joerg's suggestion of ferrite beads over gate resistors is effective, until they go PSST...BANG ;-)

Tim

I did it in a switcher, at about 60 KHz. Changed to KoolMu cores and fixed it.

Nah, no gate resistors. Gate resistors are for sissies. If you must, use a bead.

I'll never understand why people plop down a super-muscular 9A or 12A gate driver and then hang a 10ohm on its output. It's like going 20mph in a Camaro.

Yeah that's what I mean, beads :)

I've already made one prototype where a clobbered together stripline runs from the discrete gate driver (a poor man's discrete CMOS inverter followed by emitter followers) up to the MOSFET, no resistors. Pointing a finger along the circuit, you can trace the path quite accurately: 5nH at the driver, 5nH along the transmission line (a hunk of scissor-cut copper clad),

Ferrite bead stopped all that nonsense, though it got kind of warm driving only one moderately sized gate (FDP33N25 or something) at 3MHz. Waveform is slightly underdamped, so it has enough overshoot to speed up the transition without chattering or anything. A pretty simple second order RLC response, with only a little squiggly.

It'll be fun to see how it all goes at real power levels. Those 50A 600V MOSFETs take enough beating around at regular switching frequencies (~300kHz).

It concerns me that so many transistors don't specify equivalent gate spreading resistance. If they don't say in the datasheet, and they don't even approximate in the SPICE model, if they even provide a model -- heck with it! Seems to be listed more often these days though, which is good.

In first gear, no less!

Tim