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The fastest MOSFET device

thread797-212736

The fastest MOSFET device

The fastest MOSFET device

(OP)
I am looking for a MOSFET device which has the fastest tdon and tr time, the BVDSS>=800V, ID>=1A. I do not care other parameters. I only found one manufactured by Microsemi, the part# is: APT4M120K, its tdon=7.4ns, tr=4.4ns. Do you guys know other faster MOSFETs.

I am developing a circuit which needs to connect 5 MOSFETs in series to achieve high BVDSS (>4000V) but fast tdon and tr. I tried to use a transformer (one primary and 5 secondary) to directly drive the 5 MOSFETs simultaneously, only can make the tdon+tr=25ns, do you guys know other methods which can make it faster (I do not care tdoff and tf).

RE: The fastest MOSFET device

One of the main governing factors determining the turn on and off speed of a MOSFET is overcoming the gate capacitance.  The harder you drive the gate (current) the faster it will turn on or off.  What kind of drive circuit are you using?  Be prepared for a flood of ideas and options.

You didn't provide a lot of details about your application, but what you are describing sounds like it would be a better application for an SCR or IGBT given the voltages involved.



RE: The fastest MOSFET device

I would think a transformer would be a limiting factor, not a helping hand.  You're combining not only the capacitance of the gate but the inductance of the transformer windings... not good for high slew rates.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: The fastest MOSFET device

There is an IXYS part http://ixys.com/ a DE275-102N06A which is 1000 V 8 A Td=5ns Tr = 2 ns.

RE: The fastest MOSFET device

Check the board layout, keeping gate tracks wide and short, with the same length and shape if possible.  As you will have your five MOSFETs tied together like dogsled, the gate track with the longer propagation time will slow down the entire arrangement.

Good Luck!

RE: The fastest MOSFET device

What kind of transformer are you using?  You need a pulse transformer, not a normal one.  Regardless of which transformer you use, each transistor's source and drain need to get to the right voltage on turn off, which requires time.  Each transistor's capacitances need to be discharged on turn on, which also requires time.

You should look into how laser diode drivers are designed.  My recollection is that the driver was not driven by the pulse transformer directly, but had a buffer.  This is a non-trivial design exercise, you might consider subbing this to the likes of DEI: http://www.directedenergy.com/directedenergy/products/LaserDiodeDrivers/laser.htm

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: The fastest MOSFET device

Is this a Pockles cell driver ?

If it is not, then a Pockles cell driver, (or very similar technology) may be exactly what you are looking for.

Something like this perhaps:
http://www.analogmodules.com/Catalog/pockels.htm
http://www.inrad.com/pages/pockelsd.html

Here is an interesting paper from Lawrence Livermore Labs on a high voltage avalanche switcher with sub nanosecond turn on.
http://www.osti.gov/bridge/purl.cover.jsp?purl=/325425-ayLMLC/webviewable/

RE: The fastest MOSFET device

I built one of those back in college.  Had no idea there was a "market" for the drivers. !!

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: The fastest MOSFET device

I believe something fairly similar to this is also often used in ground penetrating radar.

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