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dave cox · 27th Jul 2020, 10:50 am

Andy, good detective work! As you discovered that gate resistor is the only thing that turns the MOSFET on.

I'm a bit surprised 330k didn't turn the MOSFET fully on, maybe its a bit damaged! If you go below 100k the power dissipation in the R and Q could get a little high when you dial DOWN the output voltage so beware. I notice the basic Sussex uses 470k in series with a 500k pot on the gate ...

dc

27th Jul 2020, 10:50 am	#70
dave cox Nonode Join Date: Jan 2009 Location: Bristol, UK. Posts: 2,062	Re: High voltage regulator circuit. Andy, good detective work! As you discovered that gate resistor is the only thing that turns the MOSFET on. I'm a bit surprised 330k didn't turn the MOSFET fully on, maybe its a bit damaged! If you go below 100k the power dissipation in the R and Q could get a little high when you dial DOWN the output voltage so beware. I notice the basic Sussex uses 470k in series with a 500k pot on the gate ... dc