Characteristics of Digital ICs

1.Operating speed:

Speed of a logic gate depends upon the time that elapses between the application of a signal to an input terminal and the resulting change in logical state at the output terminal.It takes into consideration the transition time(rise and fall duration of  a pulse) and propagation delays. Both of these time depend upon  the loading and increase with the increase in load.The more  inputs are attached to the output of a logic gate,the more load is to be handled by that output.High operating speed is usually the main requirement of Digital ICs.

2.Fan-In:

The fan-in of a logic gate is defined as the number of inputs(coming from similar circuits)that it can handle property.

3.Fan-out:

In general, a logic circuit is required to drive several logic inputs.The fan-out(also sometimes called the loading factor) is defines as the maximum number of standard logic inputs that an output can drive reliably.For example,a logic gate that is specified to have a fan-out of 8 standard logic inputs.If this number exceeds,the output logic-level voltages cannot be guaranteed.

4.Power Dissipation:

This is the amount of power dissipated in an IC.It is determined by the current,Icc,that it draws from the Vcc supply and equal Vcc Icc where Icc is average value of Icc (0) and Icc(1).This power is specified in mW. Lower power dissipation is desirable feature for any IC.

5.Noise Immunity:

stray electric and magnetic fields can induce voltage on the connecting wires between logic circuits.These unwanted, spurious signals are known as noise and can sometimes lead to false triggering of logic levels in the circuit.The noise immunity of a logic circuits refers to the circuit's ability to tolerate noise voltage on its inputs. A quantitative measure of noise immunity is called the noise margin.Higher the noise margin,better the logic circuit.