What are the characteristics of digital ICs used to compute their performance?

Ans:

Characteristics of Digital Integrated Circuits

1. Speed of operation:  The Speed of operation of a digital circuit is given in terms of the propagation delay time. The input delay times and output delay times can be demonstrated as:

The delay times are measured in between the 50% voltage levels of input and output wave forms. Here two delay times those are t

_phl, while the output goes from the high state to low state and t_phl, while output goes from low state to high state.

2. Power Dissipation: It is the amount of power dissipated in an IC. It is determined through the current, ICC that this draws from the V_cc supply and is provided by V_cc x I_cc. I_cc is the av value of I_CC [O] and I_CC [1]. This is specified in mW.

3. Figure of merit: For digital IC, this is explained as the product of speed and power. This is specified in Pico joules i.e. ns x mw= pj. The low value of speed power product is required.

4. Fan Out: It is the no of the same gates that can be driven by a gate. High fan out is beneficial, as this reduces the requirement for additional drivers to drive more gates.

5. Noise Immunity: Stray electric and magnetic fields make unnecessary voltages termed as noise, on the connecting wires in between logic circuits. It may cause the voltage at the input to a logic circuit to drop below V_ih or fuse above V_il and may generate unwanted operation. The circuit's capability to tolerate noise signals is termed to as the noise immunity.

6. Operating Temperature: A range of temperature wherein an IC functions properly should be identified. The accepted temperature range for consumer IC' s are from 0 to 70 degree C and for industrial applications [from -55° C to +125° C for military applications].