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In computer engineering, a logic family is one of two related concepts: * A logic family of monolithic digital
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny M ...
devices is a group of electronic
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 constructed using one of several different designs, usually with compatible
logic level In digital circuits, a logic level is one of a finite number of states that a digital signal can inhabit. Logic levels are usually represented by the voltage difference between the signal and ground, although other standards exist. The range of ...
s and power supply characteristics within a family. Many logic families were produced as individual components, each containing one or a few related basic logical functions, which could be used as "building-blocks" to create systems or as so-called "glue" to interconnect more complex integrated circuits. * A logic family may also be a set of techniques used to implement logic within
VLSI Very large-scale integration (VLSI) is the process of creating an integrated circuit (IC) by combining millions or billions of MOS transistors onto a single chip. VLSI began in the 1970s when MOS integrated circuit (Metal Oxide Semiconductor) ...
integrated circuits An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
such as central processors, memories, or other complex functions. Some such logic families use static techniques to minimize design complexity. Other such logic families, such as
domino logic Domino logic is a CMOS-based evolution of the dynamic logic techniques based on either PMOS or NMOS transistors. It allows a rail-to-rail logic swing. It was developed to speed up circuits, solving the premature cascade problem, typically by ins ...
, use clocked dynamic techniques to minimize size,
power consumption Electric energy consumption is the form of energy consumption that uses electrical energy. Electric energy consumption is the actual energy demand made on existing electricity supply for transportation, residential, industrial, commercial, and ot ...
and delay. Before the widespread use of integrated circuits, various solid-state and vacuum-tube logic systems were used but these were never as standardized and interoperable as the integrated-circuit devices. The most common logic family in modern
semiconductor devices A semiconductor device is an electronic component that relies on the electronic properties of a semiconductor material (primarily silicon, germanium, and gallium arsenide, as well as organic semiconductors) for its function. Its conductivity l ...
is
metal–oxide–semiconductor 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 ...
(MOS) logic, due to low power consumption, small transistor sizes, and high
transistor density The transistor count is the number of transistors in an electronic device (typically on a single substrate or "chip"). It is the most common measure of integrated circuit complexity (although the majority of transistors in modern microprocessors ...
.


Technologies

The list of packaged building-block logic families can be divided into categories, listed here in roughly chronological order of introduction, along with their usual abbreviations: *
Resistor–transistor logic Resistor–transistor logic (RTL) (sometimes also transistor–resistor logic (TRL)) is a class of digital circuits built using resistors as the input network and bipolar junction transistors (BJTs) as switching devices. RTL is the earliest class of ...
(RTL) ** Direct-coupled transistor logic (DCTL) ** Direct-coupled unipolar transistor logic (DCUTL) ** Resistor–capacitor–transistor logic (RCTL) *
Emitter-coupled logic In electronics, emitter-coupled logic (ECL) is a high-speed integrated circuit bipolar transistor logic family. ECL uses an overdriven bipolar junction transistor (BJT) differential amplifier with single-ended input and limited emitter current to ...
(ECL) ** Positive emitter-coupled logic (PECL) ** Low-voltage PECL (LVPECL) ** Complementary transistor micrologic (CTuL) *
Diode–transistor logic Diode–transistor logic (DTL) is a class of digital circuits that is the direct ancestor of transistor–transistor logic. It is called so because the logic gating function (e.g., AND) is performed by a diode network and the amplifying functio ...
(DTL) ** Complemented transistor diode logic (CTDL) **
High-threshold logic High-threshold logic (HTL), also known as ''low-speed logic'' (''LSL'') or ''high-level logic'' (''HLL''), is a variant of diode–transistor logic used in environments where noise is very high. Operation The threshold values at the input to a ...
(HTL) *
Transistor–transistor logic Transistor–transistor logic (TTL) is a logic family built from bipolar junction transistors. Its name signifies that transistors perform both the logic function (the first "transistor") and the amplifying function (the second "transistor"), as opp ...
(TTL) * Metal–oxide–semiconductor (MOS) logic ** P-type MOS (PMOS) logic ** N-type MOS (NMOS) logic ***
Depletion-load NMOS logic In integrated circuits, depletion-load NMOS is a form of digital logic family that uses only a single power supply voltage, unlike earlier NMOS (n-type metal-oxide semiconductor) logic families that needed more than one different power supply v ...
*** High-density NMOS (
HMOS In integrated circuits, depletion-load NMOS is a form of digital logic family that uses only a single power supply voltage, unlike earlier NMOS (n-type metal-oxide semiconductor) logic families that needed more than one different power supply v ...
) ** Complementary MOS (CMOS) logic ** Bipolar MOS (BiMOS) logic *** Bipolar CMOS (BiCMOS) *
Integrated injection logic Integrated injection logic (IIL, I2L, or I2L) is a class of digital circuits built with multiple collector bipolar junction transistors (BJT). When introduced it had speed comparable to TTL yet was almost as low power as CMOS, making it ideal for ...
(I2L) *
Gunning transceiver logic Gunning transceiver logic (GTL) is a type of logic signaling used to drive electronic backplane buses. It has a voltage swing between 0.4 volts and 1.2 volts—much lower than that used in TTL and CMOS logic—and symmetrical parallel resistive t ...
(GTL) The families (RTL, DTL, and ECL) were derived from the logic circuits used in early computers, originally implemented using discrete components. One example is the
Philips Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...
NORBIT In electronics, the NORBIT family of modules is a very early form (since 1960) of digital logic developed by Philips (and also provided through and Mullard) that uses modules containing discrete components to build logic function blocks in resi ...
family of logic building blocks. The PMOS and I2L logic families were used for relatively short periods, mostly in special purpose custom
large-scale integration An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny M ...
circuits devices and are generally considered obsolete. For example, early digital clocks or electronic calculators may have used one or more PMOS devices to provide most of the logic for the finished product. The
F14 CADC The F-14's Central Air Data Computer, also abbreviated as CADC, computes altitude, vertical speed, air speed, and mach number from sensor inputs such as pitot and static pressure and temperature. Earlier air data computer systems were electromech ...
,
Intel 4004 The Intel 4004 is a 4-bit central processing unit (CPU) released by Intel Corporation in 1971. Sold for US$60, it was the first commercially produced microprocessor, and the first in a long line of Intel CPUs. The 4004 was the first signific ...
, Intel 4040, and
Intel 8008 The Intel 8008 ("''eight-thousand-eight''" or "''eighty-oh-eight''") is an early byte-oriented microprocessor designed by Computer Terminal Corporation (CTC), implemented and manufactured by Intel, and introduced in April 1972. It is an 8-bit ...
microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circ ...
s and their support chips were PMOS. Of these families, only ECL, TTL, NMOS, CMOS, and BiCMOS are currently still in widespread use. ECL is used for very high-speed applications because of its price and power demands, while
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 ...
is mainly used in
VLSI Very large-scale integration (VLSI) is the process of creating an integrated circuit (IC) by combining millions or billions of MOS transistors onto a single chip. VLSI began in the 1970s when MOS integrated circuit (Metal Oxide Semiconductor) ...
circuits applications such as CPUs and memory chips which fall outside of the scope of this article. Present-day "building block" logic gate ICs are based on the ECL, TTL, CMOS, and BiCMOS families.


Resistor–transistor logic (RTL)

Class of
digital circuit In theoretical computer science, a circuit is a model of computation in which input values proceed through a sequence of gates, each of which computes a function. Circuits of this kind provide a generalization of Boolean circuits and a mathematical ...
s built using
resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active ...
s as the input network and
bipolar junction transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar ...
s (BJTs) as switching devices. The Atanasoff–Berry Computer used resistor-coupled
vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. The type kn ...
logic circuits similar to RTL. Several early
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 ...
ized computers (e.g.,
IBM 1620 The IBM 1620 was announced by IBM on October 21, 1959, and marketed as an inexpensive scientific computer. After a total production of about two thousand machines, it was withdrawn on November 19, 1970. Modified versions of the 1620 were used as ...
, 1959) used RTL, where it was implemented using discrete components. A family of simple resistor–transistor logic integrated circuits was developed at
Fairchild Semiconductor Fairchild Semiconductor International, Inc. was an American semiconductor company based in San Jose, California. Founded in 1957 as a division of Fairchild Camera and Instrument, it became a pioneer in the manufacturing of transistors and of in ...
for the
Apollo Guidance Computer The Apollo Guidance Computer (AGC) was a digital computer produced for the Apollo program that was installed on board each Apollo command module (CM) and Apollo Lunar Module (LM). The AGC provided computation and electronic interfaces for guida ...
in 1962.
Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globall ...
soon introduced its own family of RTL. A variant with integrated capacitors, RCTL, had increased speed, but lower immunity to noise than RTL. This was made by Texas Instruments as their "51XX" series.


Diode–transistor logic (DTL)

Class of digital circuits in which the logic gating function (e.g., AND) is performed by a diode network and the amplifying function is performed by a transistor.
Diode logic Diode logic (DL), or diode-resistor logic (DRL), is the construction of Boolean logic gates from diodes. Diode logic was used extensively in the construction of early computers, where semiconductor diodes could replace bulky and costly active v ...
was used with vacuum tubes in the earliest electronic computers in the 1940s including
ENIAC ENIAC (; Electronic Numerical Integrator and Computer) was the first programmable, electronic, general-purpose digital computer, completed in 1945. There were other computers that had these features, but the ENIAC had all of them in one pac ...
. Diode–transistor logic (DTL) was used in the
IBM 608 The IBM 608 Transistor Calculator, a plugboard-programmable unit, was the first IBM product to use transistor circuits without any vacuum tubes and is believed to be the world's first all-transistorized calculator to be manufactured for the comme ...
which was the first all-transistorized computer. Early transistorized computers were implemented using discrete transistors, resistors, diodes and capacitors. The first diode–transistor logic family of integrated circuits was introduced by
Signetics Signetics Corporation was an American electronics manufacturer specifically established to make integrated circuits. Founded in 1961, they went on to develop a number of early microprocessors and support chips, as well as the widely used 555 time ...
in 1962. DTL was also made by Fairchild and Westinghouse. A family of diode logic and diode–transistor logic integrated circuits was developed by
Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globall ...
for the
D-37C The D-37C (D37C) is the computer component of the all-inertial NS-17 Missile Guidance Set (MGS) for accurately navigating to its target thousands of miles away. The NS-17 MGS was used in the Minuteman II (LGM-30F) ICBM. The MGS, originally designed ...
Minuteman II Guidance Computer in 1962, but these devices were not available to the public. A variant of DTL called "high-threshold logic" incorporated
Zener diode A Zener diode is a special type of diode designed to reliably allow current to flow "backwards" (inverted polarity) when a certain set reverse voltage, known as the ''Zener voltage'', is reached. Zener diodes are manufactured with a great var ...
s to create a large offset between logic 1 and logic 0 voltage levels. These devices usually ran off a 15 volt power supply and were found in industrial control, where the high differential was intended to minimize the effect of noise.


PMOS and NMOS logic

P-type MOS (PMOS) logic uses
p-channel The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs ( JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs contr ...
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 ...
s to implement
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 and other
digital circuit In theoretical computer science, a circuit is a model of computation in which input values proceed through a sequence of gates, each of which computes a function. Circuits of this kind provide a generalization of Boolean circuits and a mathematical ...
s. N-type MOS (NMOS) logic uses n-channel MOSFETs to implement logic gates and other digital circuits. For devices of equal current driving capability, n-channel MOSFETs can be made smaller than p-channel MOSFETs, due to p-channel charge carriers ( holes) having lower
mobility Mobility may refer to: Social sciences and humanities * Economic mobility, ability of individuals or families to improve their economic status * Geographic mobility, the measure of how populations and goods move over time * Mobilities, a conte ...
than do n-channel charge carriers (
electrons The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kno ...
), and producing only one type of MOSFET on a silicon substrate is cheaper and technically simpler. These were the driving principles in the design of
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 ...
which uses n-channel MOSFETs exclusively. However, neglecting
leakage current In electronics, leakage is the gradual transfer of electrical energy across a boundary normally viewed as insulating, such as the spontaneous discharge of a charged capacitor, magnetic coupling of a transformer with other components, or flow of cu ...
, unlike CMOS logic, NMOS logic consumes power even when no switching is taking place.
Mohamed M. Atalla Mohamed M. Atalla ( ar, محمد عطاالله; August 4, 1924 – December 30, 2009) was an Egyptian-American engineer, physicist, cryptographer, inventor and entrepreneur. He was a semiconductor pioneer who made important contributions to ...
and
Dawon Kahng Dawon Kahng ( ko, 강대원; May 4, 1931 – May 13, 1992) was a Korean-American electrical engineer and inventor, known for his work in solid-state electronics. He is best known for inventing the MOSFET (metal–oxide–semiconductor field-effe ...
, after they invented the MOSFET, fabricated both pMOS and nMOS devices with a 20 µm process in 1960. Their original MOSFET devices had a gate length of 20 µm and a
gate oxide The gate oxide is the dielectric layer that separates the gate terminal of a MOSFET (metal-oxide-semiconductor field-effect transistor) from the underlying source and drain terminals as well as the conductive channel that connects source and drain ...
thickness of
100 nm The following are examples of orders of magnitude for different lengths. __TOC__ Overview Detailed list To help compare different orders of magnitude, the following list describes various lengths between 1.6 \times 10^ metres and 10^ ...
. However, the nMOS devices were impractical, and only the pMOS type were practical working devices. A more practical NMOS process was developed several years later. NMOS was initially faster than
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 ...
, thus NMOS was more widely used for computers in the 1970s. With advances in technology, CMOS logic displaced NMOS logic in the mid-1980s to become the preferred process for digital chips.


Emitter-coupled logic (ECL)

ECL uses an overdriven
bipolar junction transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar ...
(BJT) differential amplifier with single-ended input and limited emitter current. The ECL family, ECL is also known as current-mode logic (CML), was invented by IBM as current steering logic for use in the
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 ...
ized
IBM 7030 Stretch The IBM 7030, also known as Stretch, was IBM's first transistorized supercomputer. It was the fastest computer in the world from 1961 until the first CDC 6600 became operational in 1964."Designed by Seymour Cray, the CDC 6600 was almost three ti ...
computer, where it was implemented using discrete components. The first ECL logic family to be available in integrated circuits was introduced by
Motorola Motorola, Inc. () was an American multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent public companies, Motorola ...
as ''MECL'' in 1962.


Transistor–transistor logic (TTL)

In TTL logic,
bipolar junction transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar ...
s perform the logic and amplifying functions. The first transistor–transistor logic family of integrated circuits was introduced by Sylvania as ''Sylvania Universal High–Level Logic'' (SUHL) in 1963. Texas Instruments introduced the
7400 series The 7400 series of integrated circuits (ICs) are a popular logic family of transistor–transistor logic (TTL) logic chips. In 1964, Texas Instruments introduced the SN5400 series of logic chips, in a ceramic semiconductor package. A low-c ...
TTL family in 1964. Transistor–transistor logic uses bipolar transistors to form its integrated circuits. TTL has changed significantly over the years, with newer versions replacing the older types. Since the transistors of a standard TTL gate are saturated switches, minority carrier storage time in each junction limits the switching speed of the device. Variations on the basic TTL design are intended to reduce these effects and improve speed, power consumption, or both. The German physicist Walter H. Schottky formulated a theory predicting the
Schottky effect The Schottky effect or field enhanced thermionic emission is a phenomenon in condensed matter physics named after Walter H. Schottky. In electron emission devices, especially electron guns, the thermionic electron emitter will be biased negative ...
, which led to the
Schottky diode The Schottky diode (named after the German physicist Walter H. Schottky), also known as Schottky barrier diode or hot-carrier diode, is a semiconductor diode formed by the junction of a semiconductor with a metal. It has a low forward voltage ...
and later Schottky transistors. For the same power dissipation, Schottky transistors have a faster switching speed than conventional transistors because the Schottky diode prevents the transistor from saturating and storing charge; see
Baker clamp Baker clamp is a generic name for a class of electronic circuits that reduce the storage time of a switching bipolar junction transistor (BJT) by applying a nonlinear negative feedback through various kinds of diodes. The reason for slow turn-off t ...
. Gates built with Schottky transistors use more power than normal TTL and switch faster. With Low-power Schottky (LS), internal resistance values were increased to reduce power consumption and increase switching speed over the original version. The introduction of Advanced Low-power Schottky (ALS) further increased speed and reduced power consumption. A faster logic family called FAST (Fairchild Advanced Schottky TTL) (Schottky) (F) was also introduced that was faster than normal Schottky TTL.


Complementary MOS (CMOS) logic

CMOS logic gates use complementary arrangements of enhancement-mode N-channel and P-channel
field effect transistor The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs contro ...
. Since the initial devices used oxide-isolated metal gates, they were called
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 ...
(complementary metal–oxide–semiconductor logic). In contrast to TTL, CMOS uses almost no power in the static state (that is, when inputs are not changing). A CMOS gate draws no current other than leakage when in a steady 1 or 0 state. When the gate switches states, current is drawn from the power supply to charge the capacitance at the output of the gate. This means that the current draw of CMOS devices increases with switching rate (controlled by clock speed, typically). The first CMOS family of logic integrated circuits was introduced by
RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Com ...
as ''CD4000 COS/MOS'', the
4000 series The 4000 series is a CMOS logic family of integrated circuits (ICs) first introduced in 1968 by RCA. It had a supply voltage range of 5V to 20V, which is much wider than any contemporary logic family. Almost all IC manufacturers active during th ...
, in 1968. Initially CMOS logic was slower than LS-TTL. However, because the logic thresholds of CMOS were proportional to the power supply voltage, CMOS devices were well-adapted to battery-operated systems with simple power supplies. CMOS gates can also tolerate much wider voltage ranges than TTL gates because the logic thresholds are (approximately) proportional to power supply voltage, and not the fixed levels required by bipolar circuits. The required silicon area for implementing such digital CMOS functions has rapidly shrunk. VLSI technology incorporating millions of basic logic operations onto one chip, almost exclusively uses CMOS. The extremely small capacitance of the on-chip wiring caused an increase in performance by several orders of magnitude. On-chip clock rates as high as 4 GHz have become common, approximately 1000 times faster than the technology by 1970.


Lowering the power supply voltage

CMOS chips often work with a broader range of power supply voltages than other logic families. Early TTL ICs required a
power supply A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As ...
voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to mo ...
of 5V, but early CMOS could use 3 to 15V. Lowering the supply voltage reduces the charge stored on any capacitances and consequently reduces the energy required for a logic transition. Reduced energy implies less heat dissipation. The energy stored in a capacitance ''C'' and changing ''V'' volts is ½ ''CV''2. By lowering the power supply from 5V to 3.3V, switching power was reduced by almost 60 percent (
power dissipation In thermodynamics, dissipation is the result of an irreversible process that takes place in homogeneous thermodynamic systems. In a dissipative process, energy ( internal, bulk flow kinetic, or system potential) transforms from an initial form t ...
is proportional to the square of the supply voltage). Many motherboards have a voltage regulator module to provide the even lower power supply voltages required by many CPUs.


HC logic

Because of the incompatibility of the CD4000 series of chips with the previous TTL family, a new standard emerged which combined the best of the TTL family with the advantages of the CD4000 family. It was known as the 74HC (which used anywhere from 3.3V to 5V power supplies (and used logic levels relative to the power supply)), and with devices that used 5V power supplies and TTL
logic level In digital circuits, a logic level is one of a finite number of states that a digital signal can inhabit. Logic levels are usually represented by the voltage difference between the signal and ground, although other standards exist. The range of ...
s.


The CMOS–TTL logic level problem

Interconnecting any two logic families often required special techniques such as additional
pull-up resistor In electronic logic circuits, a pull-up resistor (PU) or pull-down resistor (PD) is a resistor used to ensure a known state for a signal. It is typically used in combination with components such as switches and transistors, which physically in ...
s, or purpose-built interface circuits, since the logic families may use different voltage levels to represent 1 and 0 states, and may have other interface requirements only met within the logic family. TTL logic levels are different from those of CMOS – generally a TTL output does not rise high enough to be reliably recognized as a logic 1 by a CMOS input. This problem was solved by the invention of the 74HCT family of devices that uses CMOS technology but TTL input logic levels. These devices only work with a 5V power supply. They form a replacement for TTL, although HCT is slower than original TTL (HC logic has about the same speed as original TTL).


Other CMOS families

Other CMOS circuit families within
integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny M ...
s include cascode voltage switch logic (CVSL) and
pass transistor logic In electronics, pass transistor logic (PTL) describes several logic families used in the design of integrated circuits. It reduces the count of transistors used to make different logic gates, by eliminating redundant transistors. Transistors are us ...
(PTL) of various sorts. These are generally used "on-chip" and are not delivered as building-block medium-scale or small-scale integrated circuits.


Bipolar CMOS (BiCMOS) logic

One major improvement was to combine CMOS inputs and TTL drivers to form of a new type of logic devices called BiCMOS logic, of which the LVT and ALVT logic families are the most important. The BiCMOS family has many members, including ABT logic, ALB logic, ALVT logic, BCT logic and LVT logic.


Improved versions

With HC and HCT logic and LS-TTL logic competing in the market it became clear that further improvements were needed to create the ''ideal'' logic device that combined high speed, with low power dissipation and compatibility with older logic families. A whole range of newer families has emerged that use CMOS technology. A short list of the most important family designators of these newer devices includes: * LV logic (lower supply voltage) * LVT logic (lower supply voltage while retaining TTL logic levels) * ALVT logic (an 'advanced' version of LVT logic) There are many others including AC/ACT logic, AHC/AHCT logic, ALVC logic, AUC logic, AVC logic, CBT logic, CBTLV logic, FCT logic and LVC logic (
LVCMOS Low voltage complementary metal oxide semiconductor (LVCMOS) is a low voltage class of CMOS technology digital integrated circuits. Overview To obtain better performance and lower costs, semiconductor manufacturers reduce the device geometries of i ...
).


Integrated injection logic (IIL)

The integrated injection logic (IIL or I2L) uses bipolar transistors in a current-steering arrangement to implement logic functions. It was used in some integrated circuits, but it is now considered obsolete.


Monolithic integrated circuit logic families compared

The following logic families would either have been used to build up systems from functional blocks such as flip-flops, counters, and gates, or else would be used as "glue" logic to interconnect very-large scale integration devices such as memory and processors. Not shown are some early obscure logic families from the early 1960s such as DCTL (direct-coupled transistor logic), which did not become widely available. ''Propagation delay'' is the time taken for a two-input NAND gate to produce a result after a change of state at its inputs. ''Toggle speed'' represents the fastest speed at which a J-K flip flop could operate. ''Power per gate'' is for an individual 2-input NAND gate; usually there would be more than one gate per IC package. Values are very typical and would vary slightly depending on application conditions, manufacturer, temperature, and particular type of logic circuit. ''Introduction year'' is when at least some of the devices of the family were available in volume for civilian uses. Some military applications pre-dated civilian use.


On-chip design styles

Several techniques and design styles are primarily used in designing large single-chip application-specific integrated circuits (ASIC) and CPUs, rather than generic logic families intended for use in multi-chip applications. These design styles can typically be divided into two main categories, static techniques and clocked dynamic techniques. (See static versus dynamic logic for some discussion on the advantages and disadvantages of each category).


Static logic

* Pulsed static CMOS * Differential cascode voltage switch (DCVS) * Cascode non-threshold logic (CNTL) * Pass-gate/transmission-gate logic:
pass transistor logic In electronics, pass transistor logic (PTL) describes several logic families used in the design of integrated circuits. It reduces the count of transistors used to make different logic gates, by eliminating redundant transistors. Transistors are us ...
(PTL) * Complementary pass-gate logic (CPL) * Push–pull logic * Output prediction logic (OPL) * Cascode voltage switch logic (CVSL)


Dynamic logic

*
four-phase logic Four-phase logic is a type of, and design methodology for dynamic logic. It enabled non-specialist engineers to design quite complex ICs, using either PMOS or NMOS processes. It uses a kind of 4-phase clock signal. History R. K. "Bob" Boo ...
*
domino logic Domino logic is a CMOS-based evolution of the dynamic logic techniques based on either PMOS or NMOS transistors. It allows a rail-to-rail logic swing. It was developed to speed up circuits, solving the premature cascade problem, typically by ins ...
* Footless domino * NORA/zipper logic * Multiple-output domino * Compound domino * Dual-rail domino * Self-resetting domino * Sample-set differential logic * Limited-switch dynamic logic


See also

*
4000 series The 4000 series is a CMOS logic family of integrated circuits (ICs) first introduced in 1968 by RCA. It had a supply voltage range of 5V to 20V, which is much wider than any contemporary logic family. Almost all IC manufacturers active during th ...
(commercial CMOS logic) *
7400 series The 7400 series of integrated circuits (ICs) are a popular logic family of transistor–transistor logic (TTL) logic chips. In 1964, Texas Instruments introduced the SN5400 series of logic chips, in a ceramic semiconductor package. A low-c ...
(commercial transistor-transistor logic) *
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 ...
* Pin-compatibility *
Open collector An open collector is a common type of output found on many integrated circuits (IC), which behaves like a switch that is either connected to ground or disconnected. Instead of outputting a signal of a specific voltage or current, the output sig ...


References


Further reading

*
4th ed. 1964
* * {{Logic Families