why long channel devices preferred in analog and short channel devices preferred in d

[vinodh475]

why long channel devices preferred in analog and short channel devices preferred in digital?

 

[crutschow]

Much of the low-frequency (1/F) noise generated in MOSFET devices is inversely proportional to the gate area. Thus for a desired L/W ratio, a longer longer L means a longer W giving more gate area and lower noise. And generally you want low noise in analog circuits since it affects dynamic range, whereas that noise has little effect on digital circuits. Since you always want minimum circuit area the digital circuits are built with minimum gate length.