How jfet transistors work both P-channel and N-channel jfets.

253

05:20:19

Hi guys, I liked to share with your my little knowledge. Plz if you know more about electronics, then let me be your student. I want to learn more about electronics.

published 7 years ago

hurz

7 years ago

JFets do conduct already without any help with gate voltage, here the extra source at gate 2.85V emulates this by being part of the jfet model. With some more positive it conducts better and with negative its going into off state. Check this i updated it for the bchannel jfet http://everycircuit.com/circuit/6124256529481728

binzen

7 years ago

Thanks so much Mr. Hurz for sharing your knowledge with the people.

hurz

7 years ago

Cooperative and collaborative knowledge transfer is what old engineers should do for the rest of its life! You are welcome!

sorh

7 years ago

I wouldn't connect a fet gate or transistor base to a direct power supply without a current limiting resistor. The same applies to the led.

hurz

7 years ago

@sorh, this is just a common methode to make a model of a real thing we do not have here in everycircuit as component. With this trick we shift the Vgs into a range were a mosfet type starts to behave like a JFet. Its not there if you build it.in real its just here. Anyway, in real you can do it also this way with a battery e.g. to emulate a JFet with e.g. a standard mosfet. Try that with a e.g. BS170. BTW, mosfets are voltage controlled and do not need a current to work statically!

kiani

7 years ago

So maybr limt Vgs with a zener for protection (in real life)!?

hurz

7 years ago

@binzen, you have applied a 1kOhn resistor as gate source resistance which is for a real JFet much to small. JFets have an extremly high isolation between gate and source. My example circuit uses a 1GOhm cuz its the single maximum value for EC. But actually in real the resistance must be even higher. 1k is tooooooo low. Check my circuit again and try to understand what the part of the JFET model is.

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