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 MOSFE ...
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 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 gate, ...
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 e ...
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 ...
*
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
In digital electronics, the fan-out is the number of gate inputs driven by the output of another single logic gate.
In most designs, logic gates are connected to form more complex circuits. While no logic gate input can be fed by more than one ...
*
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 variable (mathematics), variables are the truth values ''true'' and ''false'', usually denote ...
References
*
Digital Integrated Circuit Design: From VLSI Architectures to CMOS Fabrication', Hubert Kaeslin, Cambridge University Press, 2008
{{Digital systems
Logic gates
Equivalent units