Gate equivalent
Encyclopedia
A gate equivalent stands for a unit of measure which allows to specify manufacturing-technology-independent complexity of digital electronic circuits
.
For today's CMOS
technologies, the silicon area of a two-input drive-strength-one NAND
gate
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
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
s. If higher output drive strength is required, an additional output driver stage of four transistor
s is added.
Digital circuit
Digital electronics represent signals by discrete bands of analog levels, rather than by a continuous range. All levels within a band represent the same signal state...
.
For today's CMOS
CMOS
Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...
technologies, the silicon area of a two-input drive-strength-one NAND
Nand
NAND may stand for:*Nand , an Indian classical raga.*Logical NAND , a binary operation in logic.**NAND gate, an electronic gate that implements a logical NAND....
gate
Logic gate
A logic gate is an idealized or physical device implementing a Boolean function, that is, it performs a logical operation on one or more logic inputs and produces a single logic output. Depending on the context, the term may refer to an ideal logic gate, one that has for instance zero rise time and...
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
Standard cell
In semiconductor design, standard cell methodology is a method of designing application-specific integrated circuits with mostly digital-logic features. Standard cell methodology is an example of design abstraction, whereby a low-level very-large-scale integration layout is encapsulated into an...
is employed for each manufacturing technology (e.g., CMOS
CMOS
Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...
). The standard cell library
Standard cell
In semiconductor design, standard cell methodology is a method of designing application-specific integrated circuits with mostly digital-logic features. Standard cell methodology is an example of design abstraction, whereby a low-level very-large-scale integration layout is encapsulated into an...
comprises many different logic gate
Logic gate
A logic gate is an idealized or physical device implementing a Boolean function, that is, it performs a logical operation on one or more logic inputs and produces a single logic output. Depending on the context, the term may refer to an ideal logic gate, one that has for instance zero rise time and...
s, for example a NAND
Nand
NAND may stand for:*Nand , an Indian classical raga.*Logical NAND , a binary operation in logic.**NAND gate, an electronic gate that implements a logical NAND....
gate. For each logical type of logic gate
Logic gate
A logic gate is an idealized or physical device implementing a Boolean function, that is, it performs a logical operation on one or more logic inputs and produces a single logic output. Depending on the context, the term may refer to an ideal logic gate, one that has for instance zero rise time and...
, e.g., a two-input NAND
Nand
NAND may stand for:*Nand , an Indian classical raga.*Logical NAND , a binary operation in logic.**NAND gate, an electronic gate that implements a logical NAND....
, there usually exist different physical realizations in the standard cell library
Standard cell
In semiconductor design, standard cell methodology is a method of designing application-specific integrated circuits with mostly digital-logic features. Standard cell methodology is an example of design abstraction, whereby a low-level very-large-scale integration layout is encapsulated into an...
, for instance with different output drive strengths.
Basically, a two-input drive-strength-one NAND
Nand
NAND may stand for:*Nand , an Indian classical raga.*Logical NAND , a binary operation in logic.**NAND gate, an electronic gate that implements a logical NAND....
gate in CMOS
CMOS
Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...
technology consists of four transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
s. If higher output drive strength is required, an additional output driver stage of four transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
s is added.
See also
- Logic gateLogic gateA logic gate is an idealized or physical device implementing a Boolean function, that is, it performs a logical operation on one or more logic inputs and produces a single logic output. Depending on the context, the term may refer to an ideal logic gate, one that has for instance zero rise time and...
- Logic familyLogic familyIn computer engineering, a logic family may refer to 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 compatible logic levels and power supply...
- CMOSCMOSComplementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...
- NMOS logicNMOS logicN-type metal-oxide-semiconductor logic uses n-type metal-oxide-semiconductor field effect transistors to implement logic gates and other digital circuits...
- TransistorTransistorA transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
- Standard cellStandard cellIn semiconductor design, standard cell methodology is a method of designing application-specific integrated circuits with mostly digital-logic features. Standard cell methodology is an example of design abstraction, whereby a low-level very-large-scale integration layout is encapsulated into an...
- MOSFETMOSFETThe metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
- FanoutFanoutIn digital electronics, the fan-out of a logic gate output is the number of gate inputs to which it is connected.In most designs, logic gates are connected together to form more complex circuits. While no more than one logic gate output is connected to any single input, it is common for one output...
- FO4FO4Fan-out of 4 is a process independent delay metric used in digital CMOS technologies.Fan out = Cload / CinCload = total MOS gate capacitance driven by the logic gate under considerationCin = the MOS gate capacitance of the logic gate under consideration...
- Boolean logicBoolean logicBoolean algebra is a logical calculus of truth values, developed by George Boole in the 1840s. It resembles the algebra of real numbers, but with the numeric operations of multiplication xy, addition x + y, and negation −x replaced by the respective logical operations of...
- Digital circuitDigital circuitDigital electronics represent signals by discrete bands of analog levels, rather than by a continuous range. All levels within a band represent the same signal state...