What is the Difference Between NMOS and PMOS?

The main difference between NMOS and PMOS transistors lies in their construction and the type of charge carriers they use. Here are the key differences between NMOS and PMOS:

1. Construction: NMOS transistors use N-type doped semiconductors as source and drain, and P-type as the substrate, while PMOS transistors have the opposite arrangement.
2. Charge Carriers: NMOS transistors use electrons as majority carriers, while PMOS transistors use holes as majority carriers.
3. Mobility: NMOS transistors have a higher electron mobility, which is about twice that of PMOS transistors. This results in NMOS transistors having a lower RDS(on) (drain-source resistance) compared to PMOS transistors of identical size.
4. Voltage Levels: NMOS requires positive voltages to attract electrons, while PMOS requires negative voltages to attract holes.
5. Power Consumption: PMOS is a better choice for low-power applications due to its lower current draw, while NMOS is preferred for high-power applications because of its higher current draw capability.
6. Switching Speed: NMOS transistors are generally faster than PMOS transistors.
7. Noise: The ON resistance of NMOS is roughly half that of PMOS, although PMOS is less noise-prone.
8. Footprint: NMOS transistors occupy a smaller footprint than PMOS transistors for the same output current.
9. Power Requirement: When switching off, NMOS requires less power than PMOS transistors.

Both NMOS and PMOS transistors are widely used in analog and digital microelectronics, and in many applications, complementary MOS (CMOS) structures are used, which combine both NMOS and PMOS transistors.

Comparative Table: NMOS vs PMOS

The main differences between NMOS and PMOS transistors are the types of semiconductors used for source, drain, and substrate, as well as the carriers they use for conduction. Here is a table summarizing the differences between NMOS and PMOS:

Both NMOS and PMOS transistors can be used to create switches depending on the control signal and current flow. NMOS is more commonly used due to its advantages, such as higher electron mobility and faster speed compared to PMOS. However, many applications require the polarization characteristics of PMOS, and both types are widely used in analog and digital microelectronics. Complementary MOS (CMOS) is a popular structure that combines both NMOS and PMOS transistors, functioning as a digital inverter.