CMOS Vs TTL

The difference between the two Logic Styles are:

• TTL circuits utilize BJTs while CMOS circuits utilize FETs.
• CMOS allows a much higher density of logic functions in a single chip compared to TTL.
• TTL circuits consumes more power compared to CMOS circuits at rest.
•  CMOS chips are a lot more susceptible to static discharge compared to TTL chips
• Propagation delay is more in CMOS compared to TTL
• Switching Speed is More for TTL compared to CMOS.
• CMOS devices are cheaper than TTL Devices. 
• The Power Supply requirement for TTL is  3 to 15V, small fluctuations are tolerated.
• The Power Supply requirement for CMOS is  5V ±0.25V, it must be very smooth, a regulated supply.
• TTL Can handle only less frequency compared to CMOS.

Why CMOS is Slower compared to TTL?

Since TTL has very little parasitic capacitance, the time delay is very small, & TTL is faster.

MOSFETs, based on voltage operations, have much greater capacitances, the charging & discharging of which consumes time (Ref: RC time constant), hence CMOS is slower.