N-ch Mosfet characteristics

Thread Starter

Col16

Joined May 2, 2013
3
Hi there

I am looking for some assistance in understanding the Vds waveform I measure when switching off an N-ch enhancement mode power mosfet. The transistor is simply switching off a filament lamp that draws about 5A from the 12Vdc supply. The waveform attached has Vgs on channel 1 and Vds on channel 2.

I am thinking that the spike and discharge curve is due to some parasitic components of the transistor. The transistor is being driven very quickly with a 4A driver with no gate resistor.

Has anyone ever seen a similar voltage at the output that can shed some light on the cause?

Any help is much appreciated.

Thanks
 

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Papabravo

Joined Feb 24, 2006
21,159
Don't wound filaments look like tiny inductors?

Twinkle, twinkle little star,
V is equal L(di/dt)

OK so it doesn't rhyme.
 

tindel

Joined Sep 16, 2012
936
Yep - inductive kick from your current turning off so quickly. try to put some resistance on the gate to limit the turn on / turn off current.
 
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