Cause of triode mode in MOSFET
My reference text introduces the MOFSET as follows:
The text says the induced channel has uniform width as long as $v_{DS}$ is small, because in that case $v_{GD} = v_{GS} - v_{DS} approx v_{GS}$, and if this is violated, then the width of the channel near the drain decreases. I don't really understand why, nor how this is relevant to the width of the channel. Shouldn't $v_{DS}$ be uniform across the drain? Then wouldn't all components of the electric field be horizontal?
voltage transistors mosfet semiconductors
asked 4 hours ago
jeanluc
1182
add a comment |
My reference text introduces the MOFSET as follows:
The text says the induced channel has uniform width as long as $v_{DS}$ is small, because in that case $v_{GD} = v_{GS} - v_{DS} approx v_{GS}$, and if this is violated, then the width of the channel near the drain decreases. I don't really understand why, nor how this is relevant to the width of the channel. Shouldn't $v_{DS}$ be uniform across the drain? Then wouldn't all components of the electric field be horizontal?
voltage transistors mosfet semiconductors
asked 4 hours ago
jeanluc
1182
1
Read this ittc.ku.edu/~jstiles/312/handouts/… (page 5,6 ). And this also can help ittc.ku.edu/~jstiles/312/handouts/…
– G36
3 hours ago
add a comment |
My reference text introduces the MOFSET as follows:
The text says the induced channel has uniform width as long as $v_{DS}$ is small, because in that case $v_{GD} = v_{GS} - v_{DS} approx v_{GS}$, and if this is violated, then the width of the channel near the drain decreases. I don't really understand why, nor how this is relevant to the width of the channel. Shouldn't $v_{DS}$ be uniform across the drain? Then wouldn't all components of the electric field be horizontal?
voltage transistors mosfet semiconductors
asked 4 hours ago
jeanluc
1182
My reference text introduces the MOFSET as follows:
The text says the induced channel has uniform width as long as $v_{DS}$ is small, because in that case $v_{GD} = v_{GS} - v_{DS} approx v_{GS}$, and if this is violated, then the width of the channel near the drain decreases. I don't really understand why, nor how this is relevant to the width of the channel. Shouldn't $v_{DS}$ be uniform across the drain? Then wouldn't all components of the electric field be horizontal?
voltage transistors mosfet semiconductors
voltage transistors mosfet semiconductors
asked 4 hours ago
jeanluc
1182
asked 4 hours ago
jeanluc
1182
asked 4 hours ago
jeanluc
1182
asked 4 hours ago
jeanluc
1182
asked 4 hours ago
jeanluc
1182
1182
1
Read this ittc.ku.edu/~jstiles/312/handouts/… (page 5,6 ). And this also can help ittc.ku.edu/~jstiles/312/handouts/…
– G36
3 hours ago
add a comment |
1
Read this ittc.ku.edu/~jstiles/312/handouts/… (page 5,6 ). And this also can help ittc.ku.edu/~jstiles/312/handouts/…
– G36
3 hours ago
1
1
Read this ittc.ku.edu/~jstiles/312/handouts/… (page 5,6 ). And this also can help ittc.ku.edu/~jstiles/312/handouts/…
– G36
3 hours ago
Read this ittc.ku.edu/~jstiles/312/handouts/… (page 5,6 ). And this also can help ittc.ku.edu/~jstiles/312/handouts/…
– G36
3 hours ago
add a comment |
1 Answer
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The width of the conducting channel at any point is a function of the voltage between that point in the channel and the gate.
If Vds is zero, source and drain are at the same potential. So the potential at each point across the channel will also be the same (zero). The channel has constant width.
If Vds is (say) 1V, now there is a 1V potential distribution across the channel. Now the potential between gate and each point in the channel is not equal - it decreases as you get closer to the more positive end (drain). Let's say Vgs = 5V - that means that Vgd would be only 4V.
Hence the width of the conducting channel will decrease. This is what they are showing in the figure.
answered 1 hour ago
dmb
1,370412
add a comment |
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1 Answer
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1 Answer
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active
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The width of the conducting channel at any point is a function of the voltage between that point in the channel and the gate.
If Vds is zero, source and drain are at the same potential. So the potential at each point across the channel will also be the same (zero). The channel has constant width.
If Vds is (say) 1V, now there is a 1V potential distribution across the channel. Now the potential between gate and each point in the channel is not equal - it decreases as you get closer to the more positive end (drain). Let's say Vgs = 5V - that means that Vgd would be only 4V.
Hence the width of the conducting channel will decrease. This is what they are showing in the figure.
answered 1 hour ago
dmb
1,370412
add a comment |
The width of the conducting channel at any point is a function of the voltage between that point in the channel and the gate.
If Vds is zero, source and drain are at the same potential. So the potential at each point across the channel will also be the same (zero). The channel has constant width.
If Vds is (say) 1V, now there is a 1V potential distribution across the channel. Now the potential between gate and each point in the channel is not equal - it decreases as you get closer to the more positive end (drain). Let's say Vgs = 5V - that means that Vgd would be only 4V.
Hence the width of the conducting channel will decrease. This is what they are showing in the figure.
answered 1 hour ago
dmb
1,370412
add a comment |
The width of the conducting channel at any point is a function of the voltage between that point in the channel and the gate.
If Vds is zero, source and drain are at the same potential. So the potential at each point across the channel will also be the same (zero). The channel has constant width.
If Vds is (say) 1V, now there is a 1V potential distribution across the channel. Now the potential between gate and each point in the channel is not equal - it decreases as you get closer to the more positive end (drain). Let's say Vgs = 5V - that means that Vgd would be only 4V.
Hence the width of the conducting channel will decrease. This is what they are showing in the figure.
answered 1 hour ago
dmb
1,370412
The width of the conducting channel at any point is a function of the voltage between that point in the channel and the gate.
If Vds is zero, source and drain are at the same potential. So the potential at each point across the channel will also be the same (zero). The channel has constant width.
If Vds is (say) 1V, now there is a 1V potential distribution across the channel. Now the potential between gate and each point in the channel is not equal - it decreases as you get closer to the more positive end (drain). Let's say Vgs = 5V - that means that Vgd would be only 4V.
Hence the width of the conducting channel will decrease. This is what they are showing in the figure.
answered 1 hour ago
dmb
1,370412
answered 1 hour ago
dmb
1,370412
answered 1 hour ago
dmb
1,370412
answered 1 hour ago
dmb
1,370412
1,370412
add a comment |
add a comment |
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Read this ittc.ku.edu/~jstiles/312/handouts/… (page 5,6 ). And this also can help ittc.ku.edu/~jstiles/312/handouts/…
– G36
3 hours ago