Understand Mosfets (NMOS & PMOS): Why the Contradiction?

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In summary, MOSFETs (NMOS) have a source that is grounded, a drain at some positive voltage, and a gate initially at 0V. As the gate voltage increases, electrons are attracted from the source to the gate due to the E-field at the gate. The gate voltage cannot exceed the drain voltage or else the electrons will be stuck at the gate. When the gate voltage is increased sufficiently, the current reaches saturation. This understanding does not apply to PMOS, where the gate voltage can exceed the drain voltage and result in better conduction. The inversion layer is the region where an n-channel forms under the gate, allowing charge carriers to flow from source to drain. This is the key concept in understanding MOSF
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likephysics
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This is the way I understand Mosfets (NMOS)

The source is grounded, drain is at some positive voltage V, gate is 0v initially.
When gate voltage is increased and reaches Vth, electrons from source are attracted to the gate because of the E-field at the gate. When the electrons reach the gate, they see the more +ve drain terminal and move toward the drain.
The gate voltage cannot exceed the drain voltage, else the electrons would be stuck at the gate and not flow towards the drain terminal.
When the gate voltage is increased sufficiently (still below drain voltage), the current (Ids) reaches saturation.
Is my understanding correct?

If yes, why can’t I apply the same analogy to PMOS.
The contradiction is in PMOS, when the gate voltage exceeds drain voltage (0v), the Mosfet conducts even better.
The holes from source region reach the gate bcoz of –ve potential and why would they move towards the drain. Drain is at a lesser potential than gate.

And why is inversion layer called so?
 
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The inversion layer is called that because the p-type material under the gate (in an NMOS) is the region where an n-channel forms, allowing charge carriers to flow from source to drain.

This last bit is the key bit of understanding the operation of MOSFETs (Metal Oxide Semiconductor Field Effect Transistor)--with sufficient gate voltage, the electric field allows for the formation of a conduction channel between source and drain[*]. Everything else is details.


[*]At least, this is the case for enhancement-mode devices (depletion-mode devices have a channel 'built in', which is then narrowed or shut off using the gate).
 

Related to Understand Mosfets (NMOS & PMOS): Why the Contradiction?

1. What is a MOSFET and how does it work?

A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a type of transistor used in electronic devices to control the flow of electricity. It works by using an electric field to control the conductivity of a channel between the source and drain terminals, allowing it to act as an electronic switch.

2. What is the difference between NMOS and PMOS?

NMOS (N-channel MOSFET) and PMOS (P-channel MOSFET) are two different types of MOSFETs that use different types of charge carriers (electrons for NMOS and holes for PMOS) to control the flow of electricity. They also have different voltage polarities and operate in opposite modes.

3. Why is there a contradiction between NMOS and PMOS?

The contradiction between NMOS and PMOS lies in their operation modes. While NMOS is normally ON and requires a positive voltage to turn it OFF, PMOS is normally OFF and requires a negative voltage to turn it ON. This can lead to confusion if someone is not familiar with the different operating modes of these two types of MOSFETs.

4. Which type of MOSFET is better, NMOS or PMOS?

Neither NMOS nor PMOS is inherently better than the other. They both have their own advantages and disadvantages depending on the application. NMOS is faster and more efficient for switching operations, while PMOS is better for analog circuits and has a lower leakage current.

5. What are some common applications of NMOS and PMOS?

NMOS is commonly used in digital circuits, such as microprocessors, memory chips, and logic gates. PMOS is often used in analog circuits, such as amplifiers and voltage regulators. Both types of MOSFETs are also used in power supplies, motor control, and other electronic devices.

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