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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Re: Thanks for your concern, but . . . posted by Naz on May 9, 2007 at 00:30:30:
"The series (100R) that people hang off the gate is to prevent HF oscillation"
I know, but I didn't mean in series with the gate, I meant in series with the source. I've sometimes seen it described as a 'safety resistor'. I suppose it's to limit the current if the output is short-circuited (as it would be, for a short time after switching on, when the following reservoir cap has to be charged up).The time constant I had in mind was a 2.2Meg resistor, from the top of the zener (or VR tube, if you prefer) stack to the gate stopper, with a 2uF cap from the gate stopper to ground. Since the MOSFET has such a high gate impedance, a very high value of resistance can be used if required. This would cause the gate voltage to rise slowly, say about 10 seconds from 0v to the reference voltage.
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Follow Ups
- Re: Thanks for your concern, but . . . - Ray Moth 05/9/0700:52:56 05/9/07 (3)
- Re: Thanks for your concern, but . . . - Naz 06:41:47 05/9/07 (2)
- Perhaps I meant the drain! - Ray Moth 14:43:44 05/9/07 (1)
- That's what I thought ... - Naz 15:56:59 05/9/07 (0)
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