Electronics > Electronics

Square wave pulse (0-2.5kV)&(0.2-100msec)

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Afroman:
Putting several fets in series won't do anything other than blow them up.
For these kind of voltages, what you want is a suitable IGBT
http://www.fairchildsemi.com/sitesearch/fsc.jsp?command=eq&attr1=AAAFamily&attr2=IGBT+Discrete
or an SCR
(Search digikey.com)
Or make a mechanical switch somehow.
What are you trying to do anyway? It sounds like you are using a NST?

ellendort:
Why would they explode? assume i use 5 MOSFET in series each rated at 600V? My max. voltage is only 2500V.

IGBT's are very expensive.

I need to apply a constant voltage in between 2 electrodes. In the other word need to apply electric field to my load samples.

Depending from my load samples i know for sure they are categorized into 2 as below,

1)   In general my cell resistance vary from(Depending on the cell): 2000ohm-5000ohms
      Voltage(Depending on the cell): 0 - 2500V
      Time(Depending on the cell): 0.2-10msec

2)   In general my cell resistance vary from(Depending on the cell): 20ohm-200ohms
      Voltage(Depending on the cell): 0 - 500V
      Time(Depending on the cell): 0.2-100msec


Please advice

Afroman:
Putting mosfets in series simply doesn't work like that. It is not the same as capacitors. If one mosfet is off while all the others are on, kablam, you have the entire 2500V across 1 fet.

For your 2500V thing lasting only a few milliseconds and doesn't have a heavy load... just use an automotive ignition coil as a transformer to step up the voltage or something. Or build a high voltage DC supply with a large capacitance, then trigger it with an SCR.

ellendort:
Assume 5 MOSFETS are on. The entire 2500V across them and the 6th MOSFET will be used to trigger?

On building a high voltage DC supply with a large capacitance,
i was thinking of using
High voltage - single capacitor (25mfd/3.5kV)
Low voltage - Multiple capacitor's in parallel (390MFD/500V)

Please advice

Afroman:
I am telling you for the last time, you cannot put fets in series like that! You will start a fire.

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