The 10V is a hard number for both regular N-Channel and P-Channel MOSFETs. If you go more than 10 V (say 20V) the parts burn out, but the 10V can be considered an absolute number.

Except for Logic Level MOSFETs. I have looked hard for the collection I have, they are harder to get. Depending on the exact device number they can work 2.5-5.0V, which makes them extremely useful for low voltage circuits. They are the exception though.

In most cases when I use a conventional MOSFET I like to use 12V for the power supply.

While you can use them for high voltage why would you want to?

 

so basically for anything type of PMOS / NMOS config ... source follower or just the normal configuration where source is grounded for NMOS.... the Vgs will always be 10V? i think i know what you guys are on about now... thanks..

 

A Mosfet is rarely used as a source-follower because it needs its gate voltage to be much higher than its source and drain voltage for it to be fully turned on.
A Mosfet is an on-off switch when its source is grounded.
The turned on Vgs voltage of ordinary Mosfets is from 10V to the max allowed Vgs which is 20V.

 

I was working on an answer to this but it turned into something else.

 

You changed your name and made a new thread for the same circuit as before. Why?

 

You changed your name and made a new thread for the same circuit as before. Why?

I am not sure if you are thinking I am Vultac but no I was working on a response to some of Vultacs questions and got carried away so it seemed better to post in its own thread.

 

A Mosfet is rarely used as a source-follower because it needs its gate voltage to be much higher than its source and drain voltage for it to be fully turned on.
A Mosfet is an on-off switch when its source is grounded.
The turned on Vgs voltage of ordinary Mosfets is from 10V to the max allowed Vgs which is 20V.

It can be made to work. That is one of the issues I handled in my circuit.

 

Are you thanking me just in general or because you followed the link to my post, about the SMPS circuit that I worked out, while I was thinking of a response to some of the questions you were asking here?

 

Hey guys,

With the same schematic on post #197 (source follower),

I built it onto a veroboard, and I analyzed the graph of the gate Voltage pulse and source voltage pulse , any reason why my pulse is as shown instead of following the gate pulse? The blue is the gate voltage pulse, yellow is the source voltage pulse..

 

The gate has a +9.2V pulse (then why is it labelled as +15.9V on the schematic?) but the source rises only about +0.34V because the gate must be about 10V higher than the source. Then when the Mosfet is turned off the inductor causes the source to go to -0.34V.

The voltage of the gate pulse is much too low for a source-follower circuit.

 

Read through the attached application note.

It will help to explain what is needed to use an N-channel MOSFET as a high-side switch.

You will need either Adobe Reader or the Foxit Reader (both freeware downloads) to view the attachment.

 

This is the weirdest thread I've seen on the forum. Usually no one spends this much time on a person that won't read or accept what people trying to help them say.

 

thanks audio n sgt!