4.2 Levels of Integration

Digital ICs are categorized according to the number of logic gates or gate equivalent circuits that they contain.

Table 1. IC level of Integration

IC Category	Number of Gates	Example
SSI	1-12	Basic Gates, Flip-flops
MSI	13-99	Decoders, Counters
LSI	100-9999	Memory ICs, ALU
VLSI	10,000-99,9999	Microprocessors ICs
UHSI	Over 100,000

Small-Scale integration (SSI) devices contain several independent gates in a single package. The inputs and outputs of the gates are connected directly to the pins in the package. The number of gates is usually fewer than 10 and is limited by the number of pins available in the IC.

Medium-sale integration (MSI) devices have a complexity of approximately 10 to 100 gates in a single package. They usually perform specific elementary digital operation such as decoders, adders, or multiplexers.

Large scale integration (LS) devices contain between 100 and a few thousand gates in a single package. They include digital systems such as processors, memory chips, and programmable logic devices.

Very large-scale integration (VLSI) devices contain thousands of gates within a single package. Examples are large memory arrays and complex microcomputer chips. Because of their small size and low cost, VLSI devices have revolutionized the computer system design technology, giving the designer the capabilities to create structures

That previously were uneconomical.