In Section and we're looking at MOSFETs. MOSFET is an acronym for Metallic-Oxide-Semiconductor Field Effect Transistor. Isn't that a mouthful? There are four different types of MOS field effect transistors as shown in fig. all covered by the model going to be explained here. The ``First Order Model''. Chapter 7: MOS Field-Effect-Transistors. Previous chapter · Previous section where the velocity, v, equals the product of the mobility and the electric field.


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Negative mos field effect transistor will reduce current. We put a negative voltage here, it will tend to increase the resistance of the n-type channel and that would reduce current.

A more positive voltage would cause the channel to reduce and resistance and conduct lots of current. The gate is connected to aluminum which is insulated from the channel by a thin layer of silicone dioxide.

MOSFET - Wikipedia

Here we have our gate. This is where we differ greatly from a FET is we have actually a metal here. The aluminum is insulated from the channel by a mos field effect transistor of silicon dioxide. What that's going to do is there's no electrical connection between the gate and the n-type material because we have an insulator in between them, but we will be able to induce an electronic field through the material.

There is no connection between the gate and the source and drain.

Chapter 7: MOS Field-Effect-Transistors

The three layers led mos field effect transistor the device name hence we have Metallic, metallic, oxide, oxide, semiconductors, semiconductors. These three layers led to the device name. Here we have the actual schematic symbol.

We have a gate, a drain and a source and is usually connected as three. However, there is an option for a fourth connection and that would be over here. This adds to additional more control. Our main concern is going to be with the three connections.

MOS Field-Effect Transistor

This is the p-type. This is the same as N except for reversal of the material. The line with the arrow also indicates a connection between the source and the drain right here.

Again, the same thing except that materials have been reversed. With a voltage applied, current can easily flow between the terminals. Here we have the source.


Here we have the drain. They're connected to heavily doped n-type material.

The area between the source and the drain is lightly doped p-type material. There is no continuous channel between the source and the drain like we had with JFETs and with the depletion-mode.

Remember, this is enhancement-mode, this is a major difference right here. A proper polarity gate voltage mos field effect transistor be applied for current flow. We're going to need a gate voltage to get current flow and we will address that in a few slides from now.

MOSFETS - MOS Field Effect Transistors

If the Fermi level lies closer to the conduction band valence band then the semiconductor type will be of n-type p-type.

Therefore, when the gate voltage is increased in a positive sense for the given examplethis will "bend" the intrinsic energy level band so that it will curve downwards towards the valence band.

If the Fermi level lies closer to the valence band for p-typethere mos field effect transistor be a point when the Intrinsic level will start to cross the Fermi level and when the voltage reaches the threshold voltage, the intrinsic level does cross the Fermi level, and that is mos field effect transistor is known as inversion.

At that point, the surface of the semiconductor is inverted from p-type into n-type.