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Difference between CMOS and NMOS Technology
There are two most popular MOS (Metal Oxide Semiconductor) technologies namely CMOS and NMOS which are widely used in the field electronics and power electronics such as in ASICs, memories, processors, etc. Nowadays, the CMOS technology is one of the leading semiconductor technology. It is because the CMOS technology dissipates less power when compared to the bipolar and NOMOS technology.
In this tutorial, we will discuss the major differences between CMOS technology and NMOS technology. But before discussing the differences, let's get a brief overview of what the CMOS and NMOS technologies are.
What is CMOS Technology?
CMOS stands for Complementary Metal Oxide Semiconductor. The CMOS technology is widely used in manufacturing of ICs, digital logic circuits, microprocessors and microcontrollers, memories, etc. The CMOS technology is a combination of PMOS and NMOS technology.
The CMOS technology is one of the leading semiconductor technology because it consumes low power and has high immunity against electronic noise. Basically, the CMOS or Complementary Metal Oxide Semiconductor is an onboard semiconductor chip power by a battery and is used for data storage in computing devices. In a typical computer system, the system time and date and other hardware settings of a computer system are maintained by the CMOS IC.
The major advantage of a CMOS device is that it uses electrical power more efficiently. The other primary advantages of CMOS are as −
- It reduces the complexity of the circuit.
- It has high immunity against noise.
- It produces less heat.
- It has very low static power consumption.
- CMOS provides high density of logic functions on a single chip.
The CMOS technology is used in microprocessors, microcontrollers, memories, and many other digital logic circuits and analog circuits like data converters, sensors, communication devices, etc.
What is NMOS Technology?
NMOS is the abbreviation used for N-channel Metal Oxide Semiconductor. The NMOS uses N-type semiconductor material as the source and drain and a P-type semiconductor material as the substrate.
The NMOS technology is used to design a variety of microelectronic circuits that are used in logic chips and memory chips and also it is used as the part of CMOS (Complementary Metal Oxide Semiconductor) design.
In an NMOS, there is a layer, called N-channel layer, which conducts electrons between source and drain terminals. The NMOS technology is widely used in microprocessors and many other metal oxide semiconductor devices because they need smaller chip region and gives high density. Also, the NMOS technology gives high speed because they have electrons as the charge carriers that have relatively high mobility.
Difference between CMOS and NMOS Technology
Both CMOS and NMOS are widely used metal oxide semiconductor technologies in microelectronic circuits. However, there are several differences between CMOS and NMOS that are listed in the following table:
| Basis of Difference | CMOS Technology | NMOS Technology |
|---|---|---|
| Full form | CMOS stands for Complementary Metal Oxide Semiconductor. | NMOS stands for N-channel Metal Oxide Semiconductor. |
| Definition | A metal oxide semiconductor technology that combines both PMOS and NMOS technologies is called CMOS. | A metal oxide semiconductor technology that uses N-type channel between source and drain terminals is called NMOS. |
| Operation | The CMOS performs its operation by employing symmetrical as well as complementary pairs of P-type and N-type MOSFETs. | The NMOS performs its operation by making an inversion layer within a Ptype substrate. |
| Logic level | The logic level of CMOS is 0 V / 5 V. | The logic level of NMOS depends on the β ratio as well as noise margins. |
| Layout | CMOS has more regular layout. | NMOS has irregular layout. |
| Power dissipation | In case of CMOS, the power dissipation is zero, when it is in standby mode. | The power dissipates in NMOS, when its output is zero (0). |
| Power supply | For CMOS, the power supply may vary from 1.5 V to 15 V. | For NMOS, the power supply is fixed depending on VDD. |
| Packing density | CMOS has less packing density. Where, it requires 2N devices for N inputs. | The packing density of NMOS is high. It requires (N+1) devices for N inputs. |
| Load to drive ratio | CMOS has load / drive ratio 1:1 or 2:1. | NMOS has load / drive ratio 4:1. |
| Transmission gate | The transmission gate of CMOS allows to pass both ‘0’ and ‘1’ logic well. | The transmission gate of NMOS allows to pass only the logic ‘0’ well. If it pass logic ‘1’, then it will have VT drop. |
| Static power consumption | CMOS consumes low static power. | NMOS consumes relatively more static power. |
| Noise immunity | CMOS has high noise immunity. | NMOS has comparatively low noise immunity. |
| Applications | The CMOS is used to design various types of digital logic circuits, microprocessors, microcontrollers, memories, etc. | NMOS is used to design several types of digital logic circuits such as microprocessors, memory chips, and many other MOS devices. |
Conclusion
From the above comparison, it is clear that the CMOS technology is best suited for designing embedded systems. The one most significant difference between CMOS and NMOS is that the CMOS consumes low static power as compared to NMOS.
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