Advantages of TTL | Disadvantages of TTL
This page covers advantages and disadvantages of TTL. It mentions TTL advantages and TTL disadvantages over ECL and CMOS. TTL stands for Transistor Transistor Logic.
• The basic TTL logic circuit is NAND gate. It uses BJTs internally.
• Binary value of logic 1 is represented by 2.4 V (between 2.4V and Vcc ( usually 5V), must be more than 2V ) and logic 0 is represented by 0.4 V (between 0V and 0.8V, must be less than 0.8V) .
Advantages of TTL
Following points summarize TTL advantages over ECL and CMOS:
➨It is most rugged meaning least sysceptible to electrical damage.
➨It has strong drive capability.
➨It is faster in some versions.
➨TTL requires only one supply voltage unlike CMOS which needs two (i.e. Vdd and Vss). Vdd is between 3V and 16V and Vss is ground.
➨It has noise immunity better than ECL but lesser than CMOS.
➨It has power per gate of about 1-22 mW, which is in between CMOS and ECL.
➨The average propagation delay time is nominal and between 1.5 to 33 ns. This is better compare to CMOS. It is the time gate takes to change its state from high to low and vice versa. It should be as short as possible.
Disadvantages of TTL
Following points summarize TTL disadvantages over ECL and CMOS:
➨Cosumes more power compares to CMOS family and hence it is not suitable for battery powered devices.
➨It has fan out of 10 which is less compare to CMOS. Logic circuit having N fan out can drive N logic inputs.
Also refer difference between TTL ECL and CMOS>>.