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Strange high frequency push pull transformer action

J

Joerg

True, but none of that should matter, right? The Q2 winding section
is supposed to be unloaded when Q1 turns on. Essentially no current
flows in Q2, so the Vd(Q2) should match Vd(Q1) nearly exactly.

It never completely unloads, there will always be capacitances in the
transformer and in the FET.
 
E

ehsjr

You are old enough to remember the 2N3055, some of them had their TO3
cans adopt a blue tint from gross overheating, like the exhaust pipes of
a well-seasoned Harley-Davidson. Yet many of those were still good for
more rock sessions.

I thought that was how you prepped them for playing the blues. :)

Ed
 
B

Bill Sloman

You're about as stupid as they come,UsuallyWrong.

John Fields isn't spectacularly clever, but he's nowhere near as dumb
as krw, and he's certainly not AlwaysWrong, as anybody only a trifle
brighter than krw would be aware.

The name AlwaysWrong has been attached to somebody who posts under a
variety of pseudonyms, and "John Fields' isn't any of them.
 
B

Bill Sloman

So you have the peer-reviewed journal articles illustrating a medically
and economically important improvement in life quality and expectancy
resulting from the reduction or elimination of lead from electronic
circuitry, which is traditionally disposed of in landfills, where the lead
content has been proven to leach out into the nearby aquifer?

There's certainly that kind of stuff in the literature. I don't know
how tightly they've coupled lead in electronic solder to intellectual
development difficulties in kids, but the connection to lead in the
environment (and in the kids) is solid.
Socialist Solder, I like it.

You would. It's not a preference you'd want to advertise.
 
It was meant as a quip as much as anything and I apologise to krw if it
was right not taken as such.

The basis of my post is that generally companies are very sensitive to
employees suggesting that they run roughshod over their procedures
without qualification, and to be honest I'm surprised at krw's response.
If I import equipment into Europe I become responsible for it, and I
carry the can if it falls short of the legal standards it must conform
to. Therefore if I knew a supplier had employees that were boasting
they use leaded solder, I'd be concerned as it's trivial to check for
lead free solder by the likes of Trading Standards.

Good Lord, you're stupid! Read, why don't you? Then take a few
minutes to understand. *I* don't ship products to Europe, though my
company does - and manufactures there. *I* design and debug
prototypes (platforms used for future products). RoHS doesn't mean
shit to our lab. We use RoHS processes for boards because it's hard
to find anyone who doesn't do RoHS anymore, even harder to find leaded
parts, and we use the same parts that the eventual product will use,
anyway. Got it, dummy?
 
It never completely unloads, there will always be capacitances in the
transformer and in the FET.

Naturally, but nothing with a time constant long enough to pass a 30nS
square pulse.

Fred had a good idea--test the transformer out-of-circuit.

I'm looking forward to Mook telling us the solution to his puzzle.
 
T

Tim Williams

Bill Sloman said:
There's certainly that kind of stuff in the literature. I don't know
how tightly they've coupled lead in electronic solder to intellectual
development difficulties in kids,

So, no? Not even the electronics part specifically is really necessary,
but the landfill part would be good to know. Most electronics goes into
landfills (or is disposed of overseas) anyway, so it would be a
straightforward link to draw between leaded electronics and landfills.
Plus there's a lot of other rather nasty shit in those piles that would be
unattractive at best to be drinking, beyond just lead.

Now... that "overseas" part is interesting, because most 3rd world people
just burn the shit to get at the copper, releasing all manner of awful
chloro-bromo-fluoro-trans-cadaveroxyl-horribleinates which they aren't
even wearing masks for, not that a mere dust mask would even help that
much. Again, lead isn't as much of a hazard from inhalation, maybe the
dust -- but the burn piles will retain a whole lot of it, and that's not
very good for the people or the land. So give or take the disposal method
(open or closed, overseas or recycled, etc.), it would be environmentally
and morally responsible to use less toxic / more burnable/disposable
materials, in general.
but the connection to lead in the
environment (and in the kids) is solid.

When I signed the lease to this [old-ish, '50s era I believe] apartment, I
had to sign a disclaimer acknowledging it contains leaded paint. It's
definitely a good thing to be aware of. My neighbor has a little girl, be
a shame if she started eating paint chips. Every so often I hear violin
sounds from across the hall, which has the characteristic waver of an
inexperienced player, but given she's probably 8 or so, I'd guess she's
doing very well.

Tim
 
J

Joerg

Jan said:
I thought last night that perhaps he made a layout error and one FET is in the wrong way.
Something like this pad configuration:
0 0
0 0
0 0

would NOT work :)


But then he'd see an almost dead short on his +5V rail because the body
diode shunts it to GND.
 
J

Jamie

Bill said:
John Fields isn't spectacularly clever, but he's nowhere near as dumb
as krw, and he's certainly not AlwaysWrong, as anybody only a trifle
brighter than krw would be aware.

The name AlwaysWrong has been attached to somebody who posts under a
variety of pseudonyms, and "John Fields' isn't any of them.

God, you're unbearable. You didn't move to Sydney by choice, I bet
they deported you! Most likely couldn't afford any more brain dead
geezers sucking on the funds.

Jamie
 
J

John S

God, you're unbearable. You didn't move to Sydney by choice, I bet
they deported you! Most likely couldn't afford any more brain dead
geezers sucking on the funds.

Jamie

Then why are you bearing him? Go away.
 
J

Joerg

Jan said:
Trace impedance :)
Does that thing have a body diode?


All FETs have body diodes, it is an intrinsic part of the respective
semiconductor production process. The body diodes are, from a current
carrying capability, similar to the FET itself except that you have to
watch dissipation if you plan on using the body diode (I often do).
 
S

Spehro Pefhany

All FETs have body diodes, it is an intrinsic part of the respective
semiconductor production process. The body diodes are, from a current
carrying capability, similar to the FET itself except that you have to
watch dissipation if you plan on using the body diode (I often do).

All power MOSFETs (AFAIK) have body diodes, but I think mostly RF
FETs* don't and certainly JFETs don't.

Although free, the body diode is often a PITA since it has sluggish
recovery and has high voltage drop so we often parallel it with a good
diode, such as a Schottky. "FETKY" products combine the two in one
package. The diode tends also to do bad things if power connections
are reversed, often requiring some extra thought and/or protection.

*Eg. BSS83, which has a separate substrate connection. Not sure about
the dual-gate RF MOSFETs.. I think they do not as well.
 
I wish someone made a back-to-back (or belly-to-belly, depending on
your "orientation") device, to make a true isolating switch, as in...

http://www.analog-innovations.com/SED/PerfectDiodeForChargerIsolation...

                     or

http://www.analog-innovations.com/SED/OverAndReverseVoltageProtection...

like this? http://www.ti.com/lit/ds/symlink/csd75301w1015.pdf

but I don't see much of a need, there are plenty of dual fet in so8
and
smaller available

-Lasse
 
J

Joerg

Spehro said:
All power MOSFETs (AFAIK) have body diodes, but I think mostly RF
FETs* don't and certainly JFETs don't.

Although free, the body diode is often a PITA since it has sluggish
recovery and has high voltage drop so we often parallel it with a good
diode, such as a Schottky. "FETKY" products combine the two in one
package. The diode tends also to do bad things if power connections
are reversed, often requiring some extra thought and/or protection.

A Schottky is a problem because it must be huge. One trick I sometimes
use is to make sure the FET comes back on when the body diode wants to
conduct but lets go when the current approaches zero. Can be a
white-knuckle ride though, must be done with care. If someone built a
very fast deive for that they could make lots of money. The usual ones
are sluggish, one would need 10nsec, 20nsec max.

*Eg. BSS83, which has a separate substrate connection. Not sure about
the dual-gate RF MOSFETs.. I think they do not as well.

The SD5400 has that as well. A marvelous chip because it's a monolothic
array of four. And, unlike crude oil, its price has come back down to
about where it was in the 90's,
 
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