Module 4 – CMOS Chip design
Lecture 1& 2 – Logic design with CMOS: MOSFETS
as switches, Basic logic gates in CMOS, Complex
logic gates, Transmission gates: Muxes and latches
Prepared By,
Dr. V. Sherlin Solomi
AP(SG), ECE, HITS
Course Outcome (CO1)
Students will be able to Interpret how MOSFET works as
switches and to explain the types of ASICs
Learning Outcome
Students will be able to explain the MOSFET as switches,
Design complex logic gates, Muxes and latches. Apply the
learned concept to create new design
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
2
Complex logic gates, Transmission gates: Muxes
and latches
Introduction – MOS transistor
MOS transistors conduct electrical current by using an
applied voltage to move charge from the source side to the
drain side of the device
Objective – to examine the characteristics of MOS
transistors
Symbols
nMOS pMOS
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
3
Complex logic gates, Transmission gates: Muxes
and latches
MOS transistor switches
Terminals – Source, drain and gate
Gate – controls the passage of current between the source
and the drain
NMOS, PMOS – viewed as switches
1 – high voltage – Vdd (Power)
0 – low voltage – Vss (ground)
Strength of a signal is usually measured by its ability to sink
or source current
Stronger a signal, the more current it can source or sink
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
4
Complex logic gates, Transmission gates: Muxes
and latches
N – Switch & P- Switch
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
5
Complex logic gates, Transmission gates: Muxes
and latches
Complementary switch
Combining N- switch and P-switch in
parallel
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
6
Complex logic gates, Transmission gates: Muxes
and latches
CMOS inverter
CMOS gate always has
an N-switch (pull-down
array) to connect the
output to 0 and a P-
switch (pull-up array) to
connect the output to 1
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
7
Complex logic gates, Transmission gates: Muxes
and latches
Combinational logic - Series connection
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
8
Complex logic gates, Transmission gates: Muxes
and latches
Combinational logic – Parallel
connection
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
9
Complex logic gates, Transmission gates: Muxes
and latches
Series/parallel connection of switches
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
10
Complex logic gates, Transmission gates: Muxes
and latches
CMOS NAND gate
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
11
Complex logic gates, Transmission gates: Muxes
and latches
CMOS NOR gate
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
12
Complex logic gates, Transmission gates: Muxes
and latches
Compound gates
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
13
Complex logic gates, Transmission gates: Muxes
and latches
Compound gates
1. Construct transistor switch gate for the function
F=
2. F = implements a complemented carry function. Design a
complementary CMOS gate to perform this function
3. Sketch a 3-input CMOS NOR gate
4. Sketch a transistor-level schematic for a single stage
CMOS logic gate for each of the following functions:
a. Y=
b. Y=
c. Y=
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
14
Complex logic gates, Transmission gates: Muxes
and latches
Multiplexer
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
15
Complex logic gates, Transmission gates: Muxes
and latches
CMOS flipflop
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
16
Complex logic gates, Transmission gates: Muxes
and latches
Thank you
Lecture 1& 2 – Logic design with CMOS:
MOSFETS as switches, Basic logic gates in CMOS,
17
Complex logic gates, Transmission gates: Muxes
and latches
