Combinational MOS Logic Circuit A. Marzuki. Topics Static Characteristic Dynamic Characteristic Stick Diagram.

Combinational MOS Logic Circuit

A. Marzuki

Topics

• Static Characteristic

• Dynamic Characteristic

• Stick Diagram

Two-Input NOR Gate

VGS,load = 0 V

VOL

k = μCox W/L for case either Driver are ON,

!VGS = VOH

for case both Driver are ON,

CMOS NOR GATEAnalysis similar to CMOS Inverter , VOL = 0 V, VOH=VDD

!VS4=VDD-VSD3

!ID3+ID4=2ID

AA

BB

!replace ID of BB with AA

CMOS TG

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

CMOS TG

EXAMPLE

Complex Logic Circuits

•OR by parallel-connected drivers.•AND by series-connected drivers.•Inversion by MOS circuit operation.

CMOS Logic Circuit

Pull down graph (NMOS)

Vertex represents node

Pull up graph: vertex is drawn with areaof pull down graph. Edge cross pull downgraph’s edge once.

Equivalency

PMOS Gate length increase, NMOS Gate width increase

CMOS NOR Gate

Discuss Example 7.2Assuming W/L for PMOS is 15 for NMOS is 10

Answer is W/L for n is 12, while p is 12.5

Dynamic Characteristics (Delay)

Capacitance? Pls read chapter 6 and chapter 3. For our case, We just Use Cout i.e. the final total capacitance.

Propagation Delay

Chapter Six

Equ

ival

ency

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.

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

GNDB

NAND2

Common Euler Path

The Euler path is defined as an uninterrupted path

that traverses each edge (branch) of the graph exactly once

Comparison

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.