CMOS technology

 

CMOS Technology:

The term CMOS stands for “Complementary Metal Oxide Semiconductor”. This is one of the most popular technology in the computer chip design industry and it is broadly used today to form integrated circuits in numerous and varied applications. Today’s computer memories, CPUs, and cell phones make use of this technology due to several key advantages. 

This technology makes use of both P channel and N channel semiconductor devices. One of the most popular MOSFET technologies available today is the Complementary MOS or CMOS technology. This is the dominant semiconductor technology for microprocessors, microcontroller chips, memories like RAM, ROM, EEPROM and application-specific integrated circuits (ASICs).

CMOS CD74HC4067

The figure shows the utilization of CMOS technology in manufacturing the digital controlled switch devices.

Advantages

The advantages of CMOS include the following.

The main benefits of CMOS over TTL are good noise margin as well as less power consumption. This is due to no straight conducting lane from VDD to GND, fall times based on the conditions of input, then the transmission of the digital signal will become easy & low cost through CMOS chips.

CMOS is used to explain the amount of memory on the motherboard of the computer that will store in the settings of BIOS. These settings mainly include the date, time, and settings of hardware
TTL is a digital logic circuit where bipolar transistors work on DC pulses. Several transistor logic gates are normally made-up of a single IC.

The outputs if CMOS drive actively in both ways

• It uses a single power supply like + VDD
• These gates are very simple
• Input impedance is high
• CMOS logic uses less power whenever it is held in a set state
• Power dissipation is negligible
• Fan out is high
• TTL compatibility
• Stability of temperature
• Noise immunity is good
• Compact
• Designing is very well
• Robust mechanically
• Logic swing is large (VDD)

Disadvantages

The disadvantages of CMOS include the following.

• Cost of CMOS will be increased once the processing steps increases, however, it can be resolved.
• packing density of CMOS is low as compared with NMOS.
• MOS chips should be secured from getting static charges by placing the leads shorted otherwise; the static charges obtained within leads will damage the chip. This problem can be solved by including protective circuits otherwise devices.
• One more drawback of the CMOS inverter is that it utilizes two transistors as opposed to one NMOS to build an inverter, which means that the CMOS uses more space over the chip as compared with the NMOS. These drawbacks are small due to the progress within the CMOS technology.

CMOS Applications

Complementary MOS processes were widely implemented and have fundamentally replaced NMOS and bipolar processes for nearly all digital logic applications. CMOS technology has been used for the following digital IC designs.

• Computer memories, CPUs
• Microprocessor designs
• Flash memory chip designing
• Used to design application-specific integrated circuits (ASICs)

References:

https://www.electronics-tutorials.ws/transistor/tran_1.html

https://en.wikipedia.org/wiki/CMOS

Author: Sara Ahmad