Evolution of TTL family. • ECL. • CMOS family and its evolution. • Overview. 2 Diode-Transistor Logic (DTL) . Scaling capabilities (large integration all MOS). Logic Families – TTL, CMOS, ECL. 10 January TTL(Transistor Transistor Logic); CMOS (Complementary MOS); ECL (Emitter Coupled Logic). DTL. (Diode Transistor Logic). – Use diodes and transistors. – Input is fed TTL. ( Transistor-Transistor Logic). – Use all transistors totem pole output. ECL. ( Emitter Coupled Logic). – Non saturated logic/Current mode logic. MOS Logic Families DTL. HTL. TTL. ECL. MOS. CMOS. Basic Gate. NOR. NOR. NAND. NAND.
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A typical 74 series IC is shown in Fig 3. Several early transistorized computers e.
Caution for using MOS devices: The logic level LOW is the voltage that drives corresponding transistor in cut-off region, while logic level HIGH drives it into saturation ttll.
Thus, voltage Vcc appears at output I. 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. This is done to minimize the effect of noise introduced by the power supply and also to protect the rcl from short-circuit that might occur accidently. CMOS chips often work with a broader range of power supply voltages than other logic families.
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. All electrical circuits must consume some power, and any change in the voltages and currents in that circuit must take at least some time. Since the transistors of a standard TTL gate are tlt switches, minority carrier storage time in each junction limits the switching speed of the device.
Wikipedia articles needing clarification cmso July It has come to existence so as to overcome the speed limitations of DTL family. The collector-base junction of T1 is back-biased and T1 operates in normal active region.
See static versus dynamic logic for some discussion on the advantages and disadvantages of each category. From Wikipedia, the free encyclopedia.
The codes used vary between manufacturers, but package details are usually included on the IC datasheet. Variations on the basic TTL design are intended to reduce these effects and improve speed, power consumption, or both. The diode will conduct only when corresponding input is LOW. However as these ICs developed, at first as SSI small scale integrated devices, with just a few transistors per chip, and then as MSI medium scale integrated devices with eccl more transistors, a problem arose ec as more gates and therefore more transistors were packed into a single IC, the scale of integration would be limited by the power dissipation of the device.
Gates built with Schottky transistors ttk more power than normal TTL and switch faster. The Web This site.
Logic Families – Digital Electronics
Texas Instruments introduced the series TTL family in Analog, and Mixed-SignalMarcel Dekker, pp. The positive supply terminal of the circuit is grounded while negative supply terminal is at negative 5. Diode logic was used with vacuum tubes in the earliest electronic computers in the s including ENIAC.
CMOS gates can also tolerate much wider voltage ranges than TTL gates because the logic thresholds are approximately proportional to power supply voltage, wcl not the fixed levels required by bipolar circuits. The use of a single family within a circuit design with direct connections between ICs enables circuit designers to produce circuits consisting mainly of ICs, with few extra coupling or biasing components.
Three inputs to the gate are applied through three diodes viz. However the laws of physics, as presently understood, say that this is not possible. RTL family is characterized by poor noise margin, poor fan-out capability, low speed and high power dissipation. Because CMOS and TTL families can now operate at similar speeds and similar power consumption, the 74HCT a CMOS sub-family compatible with TTL pinouts and voltage levels now makes it possible to easily interface both families within in a single design, so enabling the use of the best features of each family.
A “logic family” may also refer to a set of techniques used to implement logic within VLSI integrated circuits such as central processorsmemories, or other complex functions. A family of diode logic and diode—transistor logic integrated circuits was developed by Texas Instruments for the DC Minuteman II Guidance Computer inbut these devices were not available to the public. CMOS Complimentary Metal Oxide Semiconductor chips, designed for minimum power, got faster and TTL families, using bipolar transistors for optimum speed, were developed that not only increased speed but also reduced power consumption.
This means that the current draw of CMOS devices increases with switching rate controlled by clock speed, typically. Retrieved from ” https: Even for storage of device, all pins must be shorted. By lowering the power supply from 5V to 3. Hence, output is connected to GND i. As the overall performance of these families increased they also became more compatible. Although each gate only dissipates a few milliWatts, the heat generated within moe single large-scale integrated LSI circuit containing tens of thousands of transistors could potentially quickly destroy the IC.
Since the initial devices used oxide-isolated metal gates, they were called CMOS complementary metal—oxide—semiconductor logic.
Introduction year is when at least some of the devices of the family were available in volume for civilian uses. ICs of a particular family generally use a common technology, but ICs in other families, using different technologies, usually have different input and output requirements, different supply voltages, and other parameters that affect the use of digital ICs.
A variant of DTL called “high-threshold logic” incorporated Zener diodes to create a large offset between logic 1 and logic 0 voltage levels. Transistor—transistor logic uses bipolar transistors to form its integrated circuits.
Difference between TTL ECL CMOS | TTL vs ECL vs CMOS
Chip designers therefore had to try and dtp the fact that higher speeds meant more power consumption, and so some families developed, using optimum speed whilst others were developed to use the minimum of power.
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. Static Dynamic Domino logic Four-phase logic.