The saturation and breakdown regions of the NMOS FET transistor

Field Effect Transistor (FET)

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1 FET. Advantages & disadvantages
2 FET electrical characteristics
3 FET cutoff and lineal regions
4 FET saturation and breakdown regions
5 MOSFET transistors
6 MOSFET: Cutoff and Lineal regions
7 MOSFET: Saturation and Breakdown regions
8 FET biasing

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The saturation region of a N channel MOSFET transistor

The NMOSFET transistor behaves as a voltage controlled current source V_GS.

Check the following equations:

where ß = K (W/L)

In this region, the quadratic relationship between VGS and ID is shown in the left part of the picture

In a similar way to the JFET transistors, it can be used to identify, by graphical methods, the bias point of the transistors.

This method is rarely used.

The breakdown region of a N channel MOSFET transistor

A MOS transistor can be affected by the avalanche phenomena in the drain and source terminals.

The MOS transistor can also be affected by breaks in the thin oxide layer of the gate that may destroy the device.

Finally, note that the table above shows the differences in sign and direction of the currents and voltages between NMOS and PMOS transistors.