0.2MHz - 2MHz step up transformer

"Paul Jackson"

** Look under "sky hook suppliers" and "tooth fairies".

.... Phil

It's a 10:1 bandwidth range. Ferrites that are good for 2MHz don't have particularly high permeabilities, and lots of turns to make up for the low permeability of the core tend to leave you with inconveniently low self-resonance frequencies.

Do you want to design a suitable more-or-less conventional transformer? I tried it once, and a transmission line transformer made with twisted pair is what worked.

-- Bill Sloman, Nijmegen

Great. If I was there you could invite me to lunch and draw a design on a Japanese napkin ... preferably before the beers.

I can't really afford a Tek HV amp, and I only need a few hundred volts. So I will keep creeping up the food chain, one start-up company at a time.

Paul

If you were designing a power transformer, this might be the case. Typically NiZn ferrites are used, with Bmax ~ 0.3T and mu_r ~ 800, like Fair-Rite #43. These might be usable close to Bsat for small transformers, but the core loss requires Bmax < 0.1T for most power applications. Which is fine, since it doesn't take much core at 2MHz to achieve that.

But signal applications under 1W are hardly the concern of core loss. Typically, a pulse transformer is wound on the highest permeability core possible (e.g., Ferroxcube 3E5, Magnetics 'W'), which accordingly has very high losses at high frequency (complex permeability is essentially imaginary), but still has greater total permeability up to several MHz than the HF material. This means you can use simpler coil geometry, giving a higher SRF despite the higher inductance. As a bonus, the SRF is dampened by the core losses at those frequencies.

Honestly, I can make a transformer with that kind of bandwidth by sitting on a ball of wire! Typically I see >10MHz from the gate drive transformers I carelessly put together, and ~50MHz with interleaving. If more than that is required, twisted pair gets involved.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

an emitter follower perhaps? transformers are so last Tuesday...

Your computer runs off AA alkalines, I gather. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

o 10V into 50R is 2W. y

is

Typically pulse transformers are transmission line transformers wound with a twisted pair transmission line, as I pointed out in my original response - not a lot of the high frequency flux makes it into the core.

How good are they at 200kHz?

You seem to live in a different universe from mine.

-- Bill Sloman, Nijmegen

On a sunny day (Sun, 22 Jan 2012 16:58:20 -0800) it happened Joerg wrote in :

Oh, I believe it, you chiseled the bits in no?

On a sunny day (Mon, 23 Jan 2012 01:57:39 -0500) it happened Phil Hobbs wrote in :

The OP mentions'transformer'. But this sounds like a simple video output CRT driver:

+120V +5 | | R 1000 C2 R |----------||----------- 100Vp Z=1k C1 | c

----||----------- b | e NPN BF??? (video output driver) | | R 10k R 100 | | for a gain of about 10 /// ///

You could use a dozen 9V batteries :-)

Said the fake who doesn't actually do any electronics.

As good as the core. Last one was somewhere around 10kHz to 10MHz.

Likewise, a regular line transformer makes a poor audio output transformer since it might only get you 50Hz to 5kHz (typical of bobbin wound transformers), however, toroids typically go up to 200kHz with just single unit layer windings.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Right. He actually does stuff.

John

How many hundred's of Volts? There are some expensive Apex HV amps. (~$40-50)

I was trolling the TI website a few weeks ago and they have some ~$10 amps that will do up to 100V. You could maybe run two of those in a bridge.

George H.

I'm not doing any electronics at the moment, but I did enough in the past to suggest that I'm not a fake. Search on scholar.google.com for "A W Sloman" and you'll find some real stuff - as well as a fair bit of stuff that never got to production, but would have worked if it had.

-- Bill Sloman, Nijmegen

Here's my 400 volt amp, but it's fairly slow.

ftp://jjlarkin.lmi.net/HVamp.JPG

It would be cool to modify this to use low-voltage optocouplers cascoded with depletion mosfets.

John

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Single layer winding are nice - the parallel capacitance usually comes out of the order of a pF - but you don't get a lot of turns.

-- Bill Sloman, Nijmegen

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So did I. A few years ago.

-- Bill Sloman, Nijmegen

But you do need at least some funding. If it has to be a fully linear scheme your best bet might be to create a really staunch "driver from hell" with just a few ohms output impedance and then use a multi-filar ferrite transformer to get the voltage up.

There are HV-amplfiers but except for some super-expensive ones they are severely slew rate limited, won't help you here.

If you could let us know some more details about what the objective is maybe there'd be other options. For example, if it's just pulsing a piezo or PZT5H with an adjustable amplitude that does not require a clean amplfier.

--
Regards, Joerg

http://www.analogconsultants.com/

I have this background thing that runs in the back of my head and checks the math on everything. It's really annoying to read the newspaper. Journalism schools don't seem to teach advanced concepts, like the difference between an amount and a rate, or the difference between a million and a billion.

This morning's catch: somebody had men and women rate pain on a scale of 0 to 10, and concluded that women feel 20% more pain.

John