AMZ Mosfet Boost on 18v?

[Serge]

Can I run the AMZ Mosfet Boost on 18v, or would this have an impact on bias points etc?  Are there any other clean boosters that can be easily run at 18v?

[zjokka]

No, the magic about the minibooster and related designs is that they are autobiasing.
Your search term is 'muamp' 

Just plug it 18V is all components are rated for that voltage and you didn't wire up a led for 9V usage yet.

[zjokka]

oops, at least that is true for the MINIBOOSTER, not sure about the MOSFET booster,
but I'd be surprised...

Somebody please correct me...

[markm]

Why would ya need 18V on the MosFET Boost?

[Serge]

I was considering to put a Mosfet booster at the end of a Neovibe, to have a useful volume control...

[markm]

I was considering to put a Mosfet booster at the end of a Neovibe, to have a useful volume control...

Ahhhhh, I See! 

[Serge]

anyone knows if the mosfet boost can be run at 18v? are there other clean boosters that can be used for this?  i noted the mini booster already

[hairyandy]

Yes, you can run the Mosfet Boost at 18v.  You may have to re-bias, I've never done it but I did inquire at one point and Jack replied himself that running it at 18v is fine.  I would just try it and see how it works, what is there to lose?  You might want to look at MarkM's layout for his "Modified Mosfet Boost" in his layout gallery.  I've built a couple of them this way and I find the volume control to be much smoother and more useful.  I think as a volume control at the end of a Neovibe circuit that his variation would work best.

Andy

[Gus]

MAYBE change one resistor(top divider resistor make it bigger to start): however maybe you could change two or three resistors to keep the drain current the same if you wanted to do that(top divider, drain R and maybe source R). 

  If you up the power supply voltage with the STOCK values the mosfet might turn on more because the voltage divider to the gate is a higher voltage BUT the current in the source R will go up causing a greater voltage drop and reducing the gate to source voltage.  things interact so you could look at curves

So lets say you keep the stock drain and source Rs where do you want the drain voltage to power supply voltage ratio 2/3 1/2 1/3 etc...?  Knowing that calculate the voltage drop across the drain R and divide by the resistor value for the drain current
being a mosfet the drain is very close the source current use the drain current to calculate the source R voltage drop and then look at the curves for the mosfet

Mosfets operation points have been posted about in other mosfet threads.  ohms law, voltage divider, drain current are some hints.

But then again maybe you want a different Id and/or drain voltage to power supply ratio.  this is diystompboxes.com

What I would do to start is to add some resistance to the "top" of the bias voltage divider resistor to adjust the drain somewhere from 1/2 to 1/3 of the supply voltage.

Make sure the mosfet is within its power and voltage ratings

[firethorn]

I think you may have to switch out the zener as well..