What is the difference between TTL and CMOS?

TTL and CMOS are commonly used digital logic levels in Embedded systems. The modern day chips comprising Micro controller, Microprocessor, discrete ICs, Memories are all CMOS based due to advantages of CMOS. Below are the differences between CMOS and TTL logic. 

• TTL stands for Transistor Transistor Logic. This logic uses BJT at the hardware level. CMOS stands for Complementary Metal Oxide semiconductor. CMOS logic uses MOSFETs at the hardware level
• The goal of any digital circuit is to perform some logical operations. Below is the TTL logic circuit

Below is the CMOS logic circuit

• The power consumption of CMOS is lesser than TTL. This is the reason why all modern day ICs are CMOS based
• Fan out of CMOS is more than TTL which meant the number of circuits that can be connected as load to CMOS are more than TTL 
• TTL based chips are rugged and are less susceptible to ESD than CMOS
• As the parasitic capacitance of BJT is less, it switches faster than MOSFET which meant the propagation delay in CMOS is greater than BJT 
• The density of CMOS is more than TTL. This meant for a given area of the chip more logic gates of CMOS can be accommodated than TTL
• Considering that density of CMOS is higher than TTL, cost of CMOS must be lower than TTL
• CMOS has higher noise margin than TTL
• CMOS devices have higher input impedance compared to TTL devices
• The TTL and CMOS voltage levels difference is shown in the below image