Step up transformer on p channel follower

AudioGeek · 3rd November 2010, 02:19 PM

i want to run a P channel follower as input buffer on a se class a mosfet amp. Similar to the Pass design of using the Zetex ZVP3310 with a 47K resistor on gate and just a load resistor to the power supply to bias the mosfet to correct current. sooo... 20v supply - 3.5v drain to source drop is 16.5v / say 100mA is 165 ohm resistor.

think is i want to switch out this resistor for a step up transformer. specifically a 1:10. if the primary dc resistance is not 165 can i add a resistor in series to make up the difference??

also, if the secondary of this transformer is driving say a irfp240n gate and no resistor load is connected across the secondary... how do i figure out the Z ratios of this transformer? and also what the minimum primary L should be?

simulating this seems like 1H is minimum and 1K secondary resistance is max.

thanks for any help.

pieter t · 3rd November 2010, 08:10 PM

Hello Richard,

Is your circuit comparable to Susan Parker's Zeus amplifier?
She is using N channel fets in a PP source follower configuration, and an interstage step-up transformer in the sources with a step-up ratio for voltage amplification ahead of the power stage, but the idea might be the same?

Pieter

3rd November 2010, 02:19 PM	#1
AudioGeek diyAudio Member Join Date: Jan 2004 Location: Minnesota	Step up transformer on p channel follower i want to run a P channel follower as input buffer on a se class a mosfet amp. Similar to the Pass design of using the Zetex ZVP3310 with a 47K resistor on gate and just a load resistor to the power supply to bias the mosfet to correct current. sooo... 20v supply - 3.5v drain to source drop is 16.5v / say 100mA is 165 ohm resistor. think is i want to switch out this resistor for a step up transformer. specifically a 1:10. if the primary dc resistance is not 165 can i add a resistor in series to make up the difference?? also, if the secondary of this transformer is driving say a irfp240n gate and no resistor load is connected across the secondary... how do i figure out the Z ratios of this transformer? and also what the minimum primary L should be? simulating this seems like 1H is minimum and 1K secondary resistance is max. thanks for any help. __________________ It is not you... you are it.

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3rd November 2010, 08:10 PM	#2
pieter t diyAudio Member Join Date: Apr 2009	Hello Richard, Is your circuit comparable to Susan Parker's Zeus amplifier? She is using N channel fets in a PP source follower configuration, and an interstage step-up transformer in the sources with a step-up ratio for voltage amplification ahead of the power stage, but the idea might be the same? Pieter

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