Characteristics of Digital IC
Some of the important characteristics of Digital IC are listed below:
1. Speed of Operations: The speed of operation of an IC is expressed in terms of propagation delay. It is defined as the time taken for the output of a gate to change after the inputs have changed.
A logic signal always experiences a delay in going through a circuit. The two propagation delay times are defined as follows:
i. tPLH: It is the propagation delay time in going from logical LOW (0 state) to logical HIGH (1 state).
ii. tPHL: It is the propagation delay time in going from logical HIGH (1 state) to logical LOW (0 state).
2. Power Dissipation: It is a measure of the power consumed by the logic gate when fully driven by all its inputs. It is expressed in milliwatts or nanowatts. The d.c or average power dissipation is the product of the d.c supply voltage and the mean current taken from that supply.
3. Fan-in: The fan-in of a gate is the number of inputs connected to the gate without any degradation in the voltage levels.
4. Fan-out: Fan-out is the maximum number of similar logic gates that a gate can drive without any degradation in voltage levels. Very often a gate will drive several other gates. Each driven gate requires a certain current which must be supplied by the driving gate. The driving gate must be capable of supplying this current while maintaining the required voltage level.
5. Noise-immunity: It denotes an unwanted signal voltage. Noise can something cause the input voltage of a logic gate to drop below VIH (min) or rise above VIL (max) which leads to unreliable operation.
6. Operating Temperature: All IC gates are semi-conductor devices that are temperature-sensitive by nature. The operating temperature ranges for an IC vary from 0°C to +70°C for consumer and industrial applications and from -55°C to +125°C for military applications.
7. Power Supply Requirements: The amount of power and supply voltage required by an IC are the main parameters to be taken into consideration while choosing a proper power supply.