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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