fet biasing

Post new topic   Reply to topic

View previous topic View next topic Go down

most sincere thanks

Post by david1959 on Tue Jun 25, 2013 8:49 pm

Thank-you Harry,
I look forward to seeing the new projects, the death ray could be useful as I am a keen gardener too

Regards
David H

david1959

Posts : 2
Join date : 2013-06-22

View user profile

Back to top Go down

Re: fet biasing

Post by Jalex2 on Mon Jun 24, 2013 4:43 pm

Hi
Yes that would be an interesting subject.

I have done quite a lot with jfets but there is still much I don't understand about them.  I have used them for switches, voltage controlled resisters,  amps, and followers in lots of different configurations.  I just make sure I can pull the gate below or above the source depending on if it's a p channel or n channel. I use a scope to check them when I get them from my junk box. It gives me a good response when I touch the gate even when there is no bios.  There is also one thing I don't understand and thats the difference between power mos fet and jfets.  I can use a mosfet like a transistor but a Jfet won't do anything configured like that. Then there is also the fact that to me a jfet works the opposite from a transistor and is saturated where there is no bios where a transistor is basically open with no bios.   What I like about them is that there is no gate current and that can be very handy when working with very weak signals with high impedance. That's all I know and I hope to learn more.

Jalex2

Posts : 104
Join date : 2012-12-06
Age : 75
Location : Long Beach , Washington, USA

View user profile

Back to top Go down

Re: fet biasing

Post by Ivan on Mon Jun 24, 2013 6:59 am

Hi all,
FET biasing is generally a bit complicated, as many functional types of FETs exist:
- by construction: JFET, MIS (MOS) FET, MES FET;
- by polarity: N-channel, P-channel;
- whether the channel exists at Ug=0V: depletion mode, enhancement mode.
Each manufactured type combines one item from each line. BTW, depletion mode MIS types require no biasing at all. They act as voltage controlled resistors to some extent.

BR from Ivan

Ivan

Posts : 181
Join date : 2012-11-25
Location : Praha, Czechia

View user profile

Back to top Go down

Re: fet biasing

Post by vk2aav on Mon Jun 24, 2013 12:52 am

Hello Harry,

I'd be very interested in an article of FET biasing too, and especially interested in learning more about the death ray Smile.

Thanks,
Steve

vk2aav

Posts : 5
Join date : 2012-11-25
Location : Sydney, Australia

View user profile http://telecnatron.com/

Back to top Go down

Re: fet biasing

Post by Admin on Sun Jun 23, 2013 9:36 pm

Hi David,
Yes, there is a good possibility of doing something about FETs. At the moment I am occupied with two projects:

 - FET VHF-HF converter
 - "Death-Ray" - goodbye to weeds

The first of these could be a good opportunity to do a little something about FETs. No promisses, but I will try.

BR Harry

_________________
(Thanks to those who tried and couldn't make the QSO. Back on 14.200MHz Sundays from the 24th Sept.)
avatar
Admin
Admin

Posts : 439
Join date : 2012-11-24
Age : 66
Location : Märsta, Sweden

View user profile http://www.sm0vpo.com

Back to top Go down

fet biasing

Post by david1959 on Sat Jun 22, 2013 10:01 pm

after many long months of trawling the internet for information on basic electronics
i found these home brew pages by accident here i found practical and useful information on how to use valves and transistor biasing is there any possibility in the future to expand the pages to include fet biasing ?????

and a personal thanks to harry for helping me to make sense of all this electronic stuff.

regards david

david1959

Posts : 2
Join date : 2013-06-22

View user profile

Back to top Go down

Re: fet biasing

Post by Sponsored content


Sponsored content


Back to top Go down

View previous topic View next topic Back to top


Post new topic   Reply to topic
 
Permissions in this forum:
You can reply to topics in this forum