combinationallogiccircuit

1. Combinational MOS Logic
Circuit
A. Marzuki

2. Topics
• Static Characteristic
• Dynamic Characteristic
• Stick Diagram

3. Two-Input NOR Gate
VGS,load = 0 V

4. VOL
k = μCox W/L for case either Driver are ON,
!VGS = VOH
for case both Driver are ON,

5. CMOS NOR GATE
Analysis similar to CMOS Inverter , VOL = 0 V,
VOH=VDD
!VS4=VDD-VSD3
!ID3+ID4=2ID
A
B
!replace ID of B with A

6. CMOS TG
!Vout is varied.
!see current direction for
Source terminal indication

7. CMOS TG
EXAMPLE

8. Complex Logic Circuits
•OR by parallel-
connected drivers.
•AND by series-
connected drivers.
•Inversion by MOS
circuit operation.

9. CMOS Logic Circuit
Pull down graph (NMOS)
Vertex represents
node
Pull up graph: vertex is drawn with area
of pull down graph. Edge cross pull down
graph’s edge once.

10. Equivalency
PMOS Gate length
increase, NMOS Gate
width increase
CMOS NOR Gate

11. Discuss Example 7.2
Assuming W/L for PMOS is 15 for NMOS is 10
Answer is W/L for n is 12, while p is 12.5

12. Dynamic Characteristics (Delay)
Capacitance? Pls read chapter 6 and chapter 3. For our case, We just
Use Cout i.e. the final total capacitance.

13. Propagation Delay
Chapter Six
Equivalency

14. Stick Diagram
• A stick diagram is a graphical view of a
layout.
• Does show all components/vias (except
possibly tub ties), relative placement.
• Does not show exact placement, transistor
sizes, wire lengths, wire widths, tub
boundaries.

15. Stick Diagram
• Represents relative positions of transistors
• Stick diagrams help plan layout quickly
– Need not be to scale
– Draw with color pencils or dry-erase markers
In
Out
VDD
GND
Inverter
A
Out
VDD
GND
B
NAND2

16. Common Euler Path
The Euler path is defined as an uninterrupted path
that traverses each edge (branch) of the graph exactly once

17. Comparison

18. References
• S-M. Kang and Y. Leblebici ,CMOS Digital
Integrated Circuits: Analysis and Design,,
3rd edition
• Jan M. Rabaey, Anantha Chandrakasan,
and Borivoje Nikolic, Digital Integrated
Circuits: A Design Perspective, 2nd
edition, Prentice Hall, 2002.