Digital Electronics

Logic FamiliesTTL and CMOS

Logic Families Competencies61. Without references the student will state what the acronym TTL stands for with 100% accuracy.62. Without references the student will state the voltage levels acceptable to a TTL input for a logic 0 and a logic 1 with 100% accuracy.63. Without references the student will state what the acronym CMOS stands for with 100% accuracy.64. Without references the student will state the voltage levels acceptable to a CMOS input for a logic 0 and a logic 1 with 100% accuracy.65. Without references, the student will list three differences between the TTL and CMOS logic families with 100% accuracy.66. Without references the student will state what the acronym ECL stands for with 100% accuracy.

Logic Families VocabularyTTL (Transistor Transistor Logic) Integrated-circuit technology that uses the bipolar transistor as the principal circuit element.CMOS (Complimentary Metal Oxide Semiconductor) Integrated-circuit technology that uses the field-effect transistor as the principal circuit element.ECL (Emitter Coupled Logic) Integrated-circuit technology that uses the bipolar transistors configured as a differential amplifier. This eliminates saturation and improves speed but uses more power than other families.

DIODE TRANSISTOR LOGIC

LOGIC LEVELS / NOISE MARGINVoltage characteristic - defines logical 0 (LOW) or logical 1 (HIGH)Noise immunity (noise margin)- logic circuits insensitivity or resistance to undesired voltages called noise.

0%10%60%50%80%70%40%30%20%100%90%HIGHLOWHIGHLOWTTLCMOS

LOW0 to +3V for CMOS0 to +0.8V in TTL Input Voltage ProfilesINPUT VOLTAGE PROFILES- TTL AND 4000 SERIES CMOS

Undefined+3 to +7V for CMOS+0.8V to +2.0V for TTL

Undefinedlogic probe reading mayvary depending onmanufacturer

HIGH+7V to +10V - CMOS+2V to +5V - TTL

CAUTIONOutput V profile differsOther families V profile differs

+5V+10VGND

+5V

+2V

+0.8V

GNDINPUT+5V

+2.4V

+0.4VGNDOUTPUT??HIGHLOWUndefinedHIGHTTL Voltage Profiles(Left mouse click for questions and answers)TEST

OTHER DIGITAL IC SPECIFICATIONSDrive Capabilities- sometimes referred to as fan-in or fan-out.Fan out- number of inputs of a logic family that can be driven by a single output. The drive capability of outputs.Fan in- the load an input places on an output. Propagation delay- has to do with the speed of the logic element. Lower propagation delays mean higher speed which is a desirable characteristic.Power Dissipation- generally, as propagation delays decrease, power consumption and heat generation increase. CMOS is noted for low power consumption.

MOS AND CMOS ICsMOS stands for metal-oxide semiconductor. PMOS, NMOS, and CMOS are three technologies used to manufacture ICs. NMOS stands for negative-channel metal-oxide semiconductor. NMOS ICs are faster than PMOS.PMOS stands for positive-channel metal-oxide semiconductor.CMOS stands for complementary metal-oxide semiconductor. Both PMOS and NMOS devices are used it its manufacture.CMOS ICs are noted for exceptionally low power consumption.CMOS ICs were slower than bipolar digital ICs (such as TTL devices).Transmission gates or bilateral switches are unique digital devices created using CMOS technology.

1. The drive capability of logic device outputs is sometimes called ___ (fan in, fan out). It is the number of inputs of a logic family that can be driven by a single output.(Left click mouse for questions and answers)Fan Out2. CMOS devices are noted for their extremely ___ (high, low) power consumption.Low3. A logic device with a low propagation delay would be considered to be a ___ (high, low) speed device.High4. Several desirable characteristics of logic devices are good drive capabilities, low power consumption, and ___ (high, low) propagation delays.LowTEST

MOSFETMETAL OXIDE SEMICONDUCTORFIELD EFFECT TRANSISTORSP-CHANNEL ENHANCEMENT N-CHANNEL ENHANCEMENTTO TURN ON GATE MUST BELOWER THAN SOURCETO TURN ON GATE MUST BEHIGHER THAN SOURCE

MOSFETMETAL OXIDE SEMICONDUCTORFIELD EFFECT TRANSISTORS

CMOSCOMPLIMENTARYMETAL OXIDE SEMICONDUCTOR

CMOSCOMPLIMENTARYMETAL OXIDE SEMICONDUCTOR

ECLEMITTER COUPLED LOGIC

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