Digital ElectronicsDigital Electronics

Logic FamiliesTTL and CMOS

Logic Families CompetenciesLogic 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 VocabularyLogic Families Vocabulary

TTL (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 LOGICDIODE TRANSISTOR LOGIC

Y

What logic function is this circuit?

11011000

YAA

FILL IN THE TRUTH TABLE

DIODE TRANSISTOR LOGIC

B

A

0V

0V

+V5V

DIODE

DIODE

MMBT39041k

1k

LOGIC LEVELS / NOISE MARGIN

• Voltage characteristic - defines logical 0 (LOW) or logical 1 (HIGH)

• Noise immunity (noise margin)- logic circuit’s insensitivity or resistance to undesired voltages called “noise.”

Input Output

2.0 - 5.5V

LOW GND - 0.8V

HIGH 2.4 - 5.5V (3.5V typical)

GND - 0.4V (0.1V typical)

TTL Voltage Profiles Chart

0%10%

60%50%

80%70%

40%30%20%

100%90%

HIGH

LOW

HIGH

LOW

TTL CMOS

LOW0 to +3V for CMOS0 to +0.8V in TTL

Input Voltage Profiles

INPUT VOLTAGE PROFILES- TTL AND 4000 SERIES CMOS

Undefined+3 to +7V for CMOS

+0.8V to +2.0V for TTL

Undefinedlogic probe reading may

vary depending onmanufacturer

HIGH+7V to +10V - CMOS

+2V to +5V - TTL

CAUTIONOutput V profile differs

Other families V profile differs

+5V +10V

GND

H

Low

+5V

+2V

+0.8V

GND

INPUT

H

Low

+5V

+2.4V

+0.4VGND

OUTPUT

? ?Input = +4VOutput = ? ?HIGH

Input = +0.3VOutput = ? LOW

Input = +1.2VOutput = ? ?Undefined

Input = +2.2VOutput = ? ?HIGH

TTL Voltage Profiles

(Left mouse click for questions and answers)

TEST

OTHER DIGITAL IC SPECIFICATIONS

• Drive 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 ICs• MOS 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 Out

2. CMOS devices are noted for their extremely ___ (high, low) power consumption.

Low

3. A logic device with a low propagation delay would be considered to be a ___ (high, low) speed device.

High

4. Several desirable characteristics of logic devices are good drive capabilities, low power consumption, and ___ (high, low) propagation delays.

Low

TEST

MOSFETMOSFETMETAL OXIDE SEMICONDUCTORMETAL OXIDE SEMICONDUCTOR

FIELD EFFECT TRANSISTORSFIELD EFFECT TRANSISTORSP-CHANNEL ENHANCEMENTP-CHANNEL ENHANCEMENT N-CHANNEL ENHANCEMENTN-CHANNEL ENHANCEMENT

TO TURN ON GATE MUST BELOWER THAN SOURCE

TO TURN ON GATE MUST BEHIGHER THAN SOURCE

TO TURN ONGATE LOWERTHAN SOURCE

DG

S

P-MOS VoutVin

C-MOS

P-MOS

N-MOS

TO TURN ONGATE HIGHERTHAN SOURCE

G

S

D

N-MOS0V

+V5V

10k

0V

5V

+V5V

+V5V

10k

TO TURN ONGATE LOWERTHAN SOURCE

DG

S

P-MOS VoutVin

C-MOS

P-MOS

N-MOS

TO TURN ONGATE HIGHERTHAN SOURCE

G

S

D

N-MOS0V

+V5V

10k

0V

5V

+V5V

+V5V

10k

MOSFETMOSFETMETAL OXIDE SEMICONDUCTORMETAL OXIDE SEMICONDUCTOR

FIELD EFFECT TRANSISTORSFIELD EFFECT TRANSISTORS

CMOSCMOSCOMPLIMENTARYCOMPLIMENTARY

METAL OXIDE SEMICONDUCTORMETAL OXIDE SEMICONDUCTOR

CMOSCMOSCOMPLIMENTARYCOMPLIMENTARY

METAL OXIDE SEMICONDUCTORMETAL OXIDE SEMICONDUCTOR

VoutVin

C-MOS

P-MOS

N-MOS

0V

+V5V

ECLECLEMITTER COUPLED LOGICEMITTER COUPLED LOGIC