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Old 9th November 2009, 01:59 AM   #1
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Join Date: Jan 2004
Location: Minnesota
Default input impedance of mosfet question?

What is the maximum recommended input impedance for a mosfet follower?

I was thinking of a using a tube input and 1:1 IT to drive a mosfer follower. The plate resistance of the tube is 2.3K.

Also thinking along the lines of an IRFP240N output running 24vdc 3-4A quiescent current. Follower into a 1:1 output transformer.

Oh and it would be push pull from input to output.

so would a tube with 2.3K plate resistance be ok to drive the mosfet with good high frequency response?


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Old 9th November 2009, 02:52 AM   #2
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Join Date: Jan 2002
Location: Tyrone Ga. U.S.A.
You may need to post that circuite. You are going to use a 1:1 output transformer?
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Old 9th November 2009, 03:11 AM   #3
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Location: Minnesota
yep 1:1 output and 1:1 IT transformer.

both are Push Pull.

Soo.. have 1:1 input transformer with phase splitter secondary straight to tube grid. battery bias on tube.

the tube with 2.3K of plate resistance is connected to a 1:1 IT.

This is connected to the mosfet gates. bias for mosfets probably at center tap of IT secondary or some other resistor arrangement to equalize current in the Push Pull mosfets.

soo.. do i need a cathode follower to drive the mosfets or can the regular connected tube do it?

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