Assuming that the bulk NMOS device has equal source and drain doping then the effective channel length is.?
Answers
First products in Complementary Metal Oxide Silicon (CMOS) technology appeared in the market in
seventies. At the beginning, CMOS devices were reserved for logic, as they offer the highest density (in
gates/mm2
), and the lowest static power consumption. Most high‐frequency circuitry was carried out in
bipolar technology. As a result, a lot of analog functions were realized in bipolar technology. The
technology development, which is driven by digital circuits (in particular by flash memories), lead to smaller
and faster CMOS devices. At the beginning of the seventies, 1µm transistors length was considered short.
Currently, CMOS technology with 22nm channel length is available. In the last twenty years a lot of analog
circuits started to be developed in CMOS technology. In fact, the technology scaling enabled CMOS devices
at higher frequencies of working, also for the analog counterpart.
Today, CMOS and bipolar technologies are in competition over a wide frequency region up to 100GHz.
The challenge indeed, to choice the technology that fulfills best the system and circuit requirements at a
reasonable cost. Bipolar is more expensive than standard CMOS technology. Moreover, most systems and
circuits are mixed signal, i.e. they include digital and analog parts. In the past, separated integrated circuits
were dedicated to the analog (bipolar) and digital (CMOS) circuits. As analog circuits were also available in
CMOS technology, this technology started to offer the opportunity to integrate cheap, high density and
low power digital circuits, as well as analog circuits, in the same chip. This brings enormous advantages in
terms of reduced costs and smaller form factors of electronic devices. Currently, CMOS technology
dominates the market. Bipolar transistors field of applications is reduced to very high frequencies of
working.