Hello.
(Note: this is not homework, I'm not at school anymore)
I know I've been around this in the past but the lack of practicing makes things go away.
I've been reading different sources about the operating zones of MOSFETs (n-channel, enhancement mode).
There are 3 operating zones (known to me)
Cut-off, Linear and Saturation zones.
First, about this, I see some sources saying that Saturation and Linear zones are the same:
https://www.electronics-tutorials.ws/transistor/tran_7.html
Why is this said? Can I assume it is wrong or at least not accurate info?
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Then, there is another detail I'm confused about. Enhancement and Depletion modes. Despite the fact that I think I don't need this knowledge, at least for now, when it's said that the mode depends on \(\displaystyle{V_{GG}}\) applied (positive or negative), it raises a question about the requisites I'm talking about below. I'll elaborate my questions about the modes below.
------------------------------
Next thing is that different sources takes different starting points to classify the requisites to say a MOSFET is in one mode of operation or another.
Example 1:
https://www.tutorialspoint.com/basic_electronics/basic_electronics_mosfet.htm
This first example uses only words to describe the possible \(\displaystyle{V_{GS}}\) values applied to the MOSFET.
Example 2:
https://electricalvoice.com/mosfet-types-operation-and-applications/
It is similar to Example 1, but Example 1 says that even with \(\displaystyle{V_{GS} = 0}\) there will still be some current flowing from drain to source. However Example 2 says that there will be no current flowing from drain to source because there is no channel connecting both terminals. This is contradictory, at least for me, at a first glance!
Example 3:
Art of Electronics, 3rd Edition, Chapter 3, Section 3.1, A - FET curves, page 132
AoE also uses mostly word, no equations or values so that we get a more realistic and practical idea of what is going on. I don't fully disagree with what is said but I think there is huge inaccuracy (or not, that's what I'm trying to clear)
So, taking a look to what is said in the 3 examples, and knowing a bit more about the requisites for the operation modes, I am confronted with some questions I can't answer to myself.
For instance, I learned that, to turn a MOSFET ON, to the Saturation mode/region, conditions are:
\(\displaystyle{V_{GS} > V_{TH}}\) and \(\displaystyle{V_{DS} > V_{GS} - V_{TH}}\)
However, the examples only say that \(\displaystyle{V_{GS}}\) or the gate voltage must be positive with respect to the source. But if \(\displaystyle{V_{TH}}\) is, for instance, 2.4V and \(\displaystyle{V_{GS}}\) = 1V, are the above statements still true? Like, what I want to say/ask is that it is not enough that the gate voltage is positive with respect to the source. It also must be greater than the threshold voltage.
Am I wrong?
With this said, I'm not even sure how to write down the requisites for \(\displaystyle{V_{GS}}\) and \(\displaystyle{V_{DS}}\) values to get the possible operation modes.
(Note: this is not homework, I'm not at school anymore)
I know I've been around this in the past but the lack of practicing makes things go away.
I've been reading different sources about the operating zones of MOSFETs (n-channel, enhancement mode).
There are 3 operating zones (known to me)
Cut-off, Linear and Saturation zones.
First, about this, I see some sources saying that Saturation and Linear zones are the same:
https://www.electronics-tutorials.ws/transistor/tran_7.html
Why is this said? Can I assume it is wrong or at least not accurate info?
------------------------------
Then, there is another detail I'm confused about. Enhancement and Depletion modes. Despite the fact that I think I don't need this knowledge, at least for now, when it's said that the mode depends on \(\displaystyle{V_{GG}}\) applied (positive or negative), it raises a question about the requisites I'm talking about below. I'll elaborate my questions about the modes below.
------------------------------
Next thing is that different sources takes different starting points to classify the requisites to say a MOSFET is in one mode of operation or another.
Example 1:
https://www.tutorialspoint.com/basic_electronics/basic_electronics_mosfet.htm
This first example uses only words to describe the possible \(\displaystyle{V_{GS}}\) values applied to the MOSFET.
Example 2:
https://electricalvoice.com/mosfet-types-operation-and-applications/
It is similar to Example 1, but Example 1 says that even with \(\displaystyle{V_{GS} = 0}\) there will still be some current flowing from drain to source. However Example 2 says that there will be no current flowing from drain to source because there is no channel connecting both terminals. This is contradictory, at least for me, at a first glance!
Example 3:
Art of Electronics, 3rd Edition, Chapter 3, Section 3.1, A - FET curves, page 132
AoE also uses mostly word, no equations or values so that we get a more realistic and practical idea of what is going on. I don't fully disagree with what is said but I think there is huge inaccuracy (or not, that's what I'm trying to clear)
So, taking a look to what is said in the 3 examples, and knowing a bit more about the requisites for the operation modes, I am confronted with some questions I can't answer to myself.
For instance, I learned that, to turn a MOSFET ON, to the Saturation mode/region, conditions are:
\(\displaystyle{V_{GS} > V_{TH}}\) and \(\displaystyle{V_{DS} > V_{GS} - V_{TH}}\)
However, the examples only say that \(\displaystyle{V_{GS}}\) or the gate voltage must be positive with respect to the source. But if \(\displaystyle{V_{TH}}\) is, for instance, 2.4V and \(\displaystyle{V_{GS}}\) = 1V, are the above statements still true? Like, what I want to say/ask is that it is not enough that the gate voltage is positive with respect to the source. It also must be greater than the threshold voltage.
Am I wrong?
With this said, I'm not even sure how to write down the requisites for \(\displaystyle{V_{GS}}\) and \(\displaystyle{V_{DS}}\) values to get the possible operation modes.