UNIT – VCMOS LOGIC:CMOS logic levels, MOS transistors, Basic CMOS Inverter, NAND and NOR gates, CMOS AND-OR-INVERT and OR-AND-INVERT gates, Implementation of any function using CMOS logic.COMBINATIONAL CIRCUITS USING TTL 74XX ICS Study of logic gates using 74XX ICs, Four-bit parallel adder(IC 7483),Comparator(IC 7485), Decoder(IC 74138, IC 74154), BCD-to-7-segment decoder(IC 7447), Encoder(IC 74147), Multiplexer(IC74151), Demultiplexer (IC 74154).SEQUNTIAL CIRCUITS USING TTL 74XX ICS Flip Flops (IC 7474, IC 7473), Shift Registers, Universal Shift Register(IC 74194), 4- bit asynchronous binary counter(IC 7493).
CMOS LOGIC
• CMOS logic levels • MOS transistors• Basic CMOS Inverter• NAND and NOR gates• CMOS AND-OR-INVERT • OR-AND-INVERT gates• Implementation of any function using CMOS logic
INTEGRATED CIRCUIT TECHNOLOGIES FOR DIGITAL ICs
• BIPOLAR TECHNOLOGY- SSI AND MSI– TTL (WIDELY USED)– ECL
• UNIPOLAR TECHNOLOGY(MOSFET) - LSI, VLSI AND ULSI– CMOS – NMOS
TTL AND CMOS SERIES
TTL SERIES CMOS SERIES(5V and 3.3V)
• HC – HIGH SPEED CMOS• AHC- ADVANCED HIGH
SPPED CMOS• LV – LOW VOLATGE CMOS• HCT – HIGH SPEED CMOS
AND TTL COMPATIBLE
• 74 – Standard TTL (no letter)• 74S- Schottky TTL• 74AS – Advanc Schottky TTL• 74LS – Low power Schottky
TTL• 74ALS-Advanced Low power
Schottky TTL• 74F-Fast TTL
MOS OVER TTL
• INEXPENSIVE AND EASY TO FABRICATE• OCCUPIES LESS SPACE• CONSUMES LITTLE POWER• RESISTORS CAN BE CONSTRUCTED WITH
MOSFETS• ACCOMODATES MORE NO. OF ELEMENTS
THAN TTL IN SAME SPACE• SUITABLE FOR COMPLEX ICs
MOS TRANSISTORS
• DEPLETION MOSFET• ENHANCEMENT MOSFET
– PMOS- » ON(GATE VOLTAGE = LOGIC 0)» OFF(GATE VOLTAGE = LOGIC 1)» AND OPERATION IN A PARALLEL CONNECTIVITY» OR OPERATION IN A SERIES CONNECTIVITY
– NMOS- » ON(GATE VOLTAGE = LOGIC 1)» OFF(GATE VOLTAGE = LOGIC 0)» AND OPERATION IN A SERIES CONNECTIVITY» OR OPERATION IN A PARALLEL CONNECTIVITY
– BASICALLY USED AS A SWITCH
MOS TRANSISTORS
• NMOS• PMOS • CMOS
NMOS OVER PMOS
• PACKAGE DENSITY IS MORE• ABOUT THREE TIMES FASTER• MOSTLY MEMORIES, PROCESSORS AND
PERIPHERAL DEVICES ARE AVALIABLE IN NMOS• PMOS AND NMOS ARE ECONOMICAL THAN
CMOS
SYMBOL AND SWITCHING OF MOSFETs
NMOS AS RESISTOR, NAND AND NOR
NMOS CHARACTERISTICS
• INPUT IMPEDENCE HIGH• INPUT CAPACITANCE IS HIGH• INPUT CURRENT IS LOW• FANOUT IS LARGE(TYPICALLY 30)• LOW OPERATING SPEED• PROPAGATION DELAY TIME IS LARGE(50nS)• POWER DISSIPATION IS SMALL COMPARED TO
TTL (TYPICALLY 0.1mW/GATE)
PMOS TRANSISTORS AS NOR GATE
BASIC CMOS INVERTER
BASIC OPERATION OF CMOS INVERTER
CMOS NAND GATES
CMOS NOR GATE
CMOS AND-OR-INVERT• CMOS circuits can perform two levels of logic
with just a single level of transistors.• Y= AB CD
CMOS OR-AND-INVERT
• Y= A B C D
Problem
• Design CMOS transistor circuit that has functional behaviour f(z)=
• f(z)= =
.A B C
.A B C AB AC
Problems
• Design CMOS transistor circuit that has functional behaviour
1) f(z)=
2) f(z)=
3) f(z)=
A B B C
A B C
a b b c a c
CMOS LOGIC LEVELS
CMOS LOGIC LEVELS
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