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MOSFET output stage gate protection Cordell style
MOSFET output stage gate protection Cordell style
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Old 15th September 2021, 07:08 AM   #1
Lee Knatta is offline Lee Knatta  Germany
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Location: Munich, Alps
Default MOSFET output stage gate protection Cordell style


I came across slides from Bob Cordell showing details of the DH-220C amplifier. Those slides were presented during the Burning Amp convention 2016.

The output stage gate protection looks unusual. I'm pretty sure this circuit is superior to a simpler way like back to back Zeners, but I can't figure out why.

Somehow I feel stupid for asking because this is such a simple circuit, but can somebody more knowledgeable please explain it to me?
Why is this circuit any better than just back back Zeners between gates and source?

Thank you very much!
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Old 15th September 2021, 11:53 AM   #2
rsavas is offline rsavas  Canada
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Join Date: Aug 2012
Location: Georgina, Ontario
This circuit is described on p347 of Bob’s 2nd edition of designing audio power amps. It says the 220k resistors in the circuit provide about 2.7V of reverse bias to the zener diodes to reduce their capacitance

Last edited by rsavas; 15th September 2021 at 11:56 AM.
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