A gate equivalent (GE) stands for a unit of measure which allows specifying ''manufacturing-technology-independent complexity'' of
digital electronic circuits.
For today's
CMOS
Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSF ...
technologies, the silicon area of a two-input drive-strength-one
NAND gate
A gate or gateway is a point of entry to or from a space enclosed by walls. The word derived from old Norse "gat" meaning road or path; But other terms include ''yett and port''. The concept originally referred to the gap or hole in the wall ...
usually constitutes the ''technology-dependent'' unit area commonly referred to as gate equivalent.
A specification in gate equivalents for a certain circuit reflects a complexity measure, from which a corresponding silicon area can be deduced for a dedicated manufacturing technology.
In digital circuit design, a dedicated ''
standard cell
In semiconductor design, standard cell methodology is a method of designing application-specific integrated circuits (ASICs) with mostly digital-logic features. Standard cell methodology is an example of design abstraction, whereby a low-level v ...
library'' is employed for each manufacturing technology (e.g., CMOS). The standard cell library comprises many different
logic gate
A logic gate is an idealized or physical device implementing a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output. Depending on the context, the term may refer to an ideal logic ga ...
s, for example a NAND gate. For each logical type of logic gate, e.g., a two-input NAND, there usually exist different physical realizations in the standard cell library, for instance with different output drive strengths.
Basically, a two-input
drive-strength-one NAND gate in CMOS technology consists of four
transistor
upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...
s.
See also
*
Logic family
In computer engineering, a logic family is one of two related concepts:
* A logic family of monolithic digital integrated circuit devices is a group of electronic logic gates constructed using one of several different designs, usually with compati ...
*
NMOS logic
N-type metal-oxide-semiconductor logic uses n-type (-) MOSFETs (metal-oxide-semiconductor field-effect transistors) to implement logic gates and other digital circuits. These nMOS transistors operate by creating an inversion layer in a p-type t ...
*
MOSFET
The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...
*
Fanout
*
FO4
In digital electronics, Fan-out of 4 is a measure of time used in digital CMOS technologies: the gate delay of a component with a fan-out of 4.
Fan out = Cload / Cin, where
:Cload = total MOS gate capacitance driven by the logic gate under con ...
*
Boolean logic
In mathematics and mathematical logic, Boolean algebra is a branch of algebra. It differs from elementary algebra in two ways. First, the values of the variables are the truth values ''true'' and ''false'', usually denoted 1 and 0, whereas ...
References
*
Digital Integrated Circuit Design: From VLSI Architectures to CMOS Fabrication', Hubert Kaeslin, Cambridge University Press, 2008
{{Digital systems
Logic gates
Equivalent units