papasan
Enlightened
is a p-channel mosfet an NPN or a PNP transistor?. and, while i'm on the subject, what does MOSFET stand for and how do they differ from 'traditional' transistors? thanks.
silly MOSFET question...
- Thread starter papasan
- Start date
Jonathan
Enlightened
A p-channel MOSFET is more akin to a PNP transistor than to an NPN transistor, but they are different beasties by a long ways.
A FET is a 'field effect transistor'. You have a semiconductor channel, with no PN or NP junctions along it. This channel is essentially a resistor made semiconductor materials. A 'gate' manipulates an electric field across this channel, and changes the population of charge carriers available, or changes the cross section of the channel which conducts current. Essentially the 'gate' can change the resistance of the channel.
No current flows between the gate and the channel, so a FET is a _voltage_ controlled device, quite unlike a regular bipolar junction transistor in which _current_ flow through the base terminal controls the _current_ flowing between emitter and collector.
The gate electrode may be isolated from the channel by a PN junction, essentially a reverse biased diode. This sort of device is called a J-FET, or junction FET. The gate electrode may also be isolated from the channel by an insulating layer. This layer is made of metal oxide, thus Metal Oxide Semiconductor FET or MOSFET.
The reason that I said at the beginning that a p-FET is more akin to a PNP transistor is that the relative polarities of the terminal voltages are the same.
-Jon
A FET is a 'field effect transistor'. You have a semiconductor channel, with no PN or NP junctions along it. This channel is essentially a resistor made semiconductor materials. A 'gate' manipulates an electric field across this channel, and changes the population of charge carriers available, or changes the cross section of the channel which conducts current. Essentially the 'gate' can change the resistance of the channel.
No current flows between the gate and the channel, so a FET is a _voltage_ controlled device, quite unlike a regular bipolar junction transistor in which _current_ flow through the base terminal controls the _current_ flowing between emitter and collector.
The gate electrode may be isolated from the channel by a PN junction, essentially a reverse biased diode. This sort of device is called a J-FET, or junction FET. The gate electrode may also be isolated from the channel by an insulating layer. This layer is made of metal oxide, thus Metal Oxide Semiconductor FET or MOSFET.
The reason that I said at the beginning that a p-FET is more akin to a PNP transistor is that the relative polarities of the terminal voltages are the same.
-Jon
Hi Papasan,
Good resource for basic to intermediate electronic lesson ! Highly recomended !
Lessons In Electric Circuits
It is free and my recomendation is download all those books and trust me, you might need it "someday" !
Vic
Good resource for basic to intermediate electronic lesson ! Highly recomended !
Lessons In Electric Circuits
It is free and my recomendation is download all those books and trust me, you might need it "someday" !
Vic
papasan
Enlightened
excellent link, thanks. i see a chapter for JFETs and IGFETs but not MOSFETs. but definatly a good place to look through for general knowledge. i notice that alot of the chapters are labeled 'unfinished'.
second question: do all P-channel MOSFETs conduct negative voltage? doing some poking around in Digi-Key for the right transistor for a Maxam circuit and all i see are P-channels listed in -V.
does the P mean that it's controlled by positive voltage? perhaps then it only conducts negetive voltage?
** edit **
a little reading...it sounds as if a MOSFET is a type of IGFET. thanks for the link again =).
second question: do all P-channel MOSFETs conduct negative voltage? doing some poking around in Digi-Key for the right transistor for a Maxam circuit and all i see are P-channels listed in -V.
does the P mean that it's controlled by positive voltage? perhaps then it only conducts negetive voltage?
** edit **
a little reading...it sounds as if a MOSFET is a type of IGFET. thanks for the link again =).
Hi again Papasan,
Other resource, this one has Basic Introduction up to Interfacing with MOSFET.
Web EE Primers
Vic
Other resource, this one has Basic Introduction up to Interfacing with MOSFET.
Web EE Primers
Vic
remuen
Enlightened
Hi papasan
I think your question as title of this topic isn't correct
as it's not a silly question. As beginners we somehow have to learn it. And here in the CPF we have some great fellows which do help us.
As long as we admit that we know only a little most of these experts will explain us almost everything as they did in the past. In this sense your question is a good MOSFET question. Thank you that you have asked it!
I think your question as title of this topic isn't correct
As long as we admit that we know only a little most of these experts will explain us almost everything as they did in the past. In this sense your question is a good MOSFET question. Thank you that you have asked it!
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by remuen:
Hi papasan
I think your question as title of this topic isn't correct
as it's not a silly question. As beginners we somehow have to learn it. And here in the CPF we have some great fellows which do help us.
As long as we admit that we know only a little most of these experts will explain us almost everything as they did in the past. In this sense your question is a good MOSFET question. Thank you that you have asked it!
<HR></BLOCKQUOTE>
Amen.
No man is as ignorant as the one who will not ask why or how of what they do not know or understand - Lambda
Hi papasan
I think your question as title of this topic isn't correct
As long as we admit that we know only a little most of these experts will explain us almost everything as they did in the past. In this sense your question is a good MOSFET question. Thank you that you have asked it!
Amen.
No man is as ignorant as the one who will not ask why or how of what they do not know or understand - Lambda
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by vicbin:
Hi Papasan,
Good resource for basic to intermediate electronic lesson ! Highly recomended !
Lessons In Electric Circuits
It is free and my recomendation is download all those books and trust me, you might need it "someday" !
Vic<HR></BLOCKQUOTE>
I'm shamelesly bumping this to the top by pointing out that this link is outstanding..
thanks for posting it Vic
Hi Papasan,
Good resource for basic to intermediate electronic lesson ! Highly recomended !
Lessons In Electric Circuits
It is free and my recomendation is download all those books and trust me, you might need it "someday" !
Vic<HR></BLOCKQUOTE>
I'm shamelesly bumping this to the top by pointing out that this link is outstanding..
thanks for posting it Vic
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