1 Static CMOS Circuits. Ankur Agarwal 2 Static CMOS Circuits In Static CMOS circuits with n inputs, 2n transistors are needed. nMOS block is a dual of.

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Static CMOS Circuits

2Ankur Agarwal

Static CMOS Circuits

In Static CMOS circuits with n inputs, 2n transistors are needed.

nMOS block is a dual of the pMOS block. What ever is in series in nMOS, appears in

parallel in pMOS and vice versa. CMOS gates consume power only during the

transition of inputs.

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Static complementary gate structure

Pull-up and pull-down networks

pull-upnetwork

Pull-downnetwork

VDD

VSS

outinputs

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Pull-up/pull-down network design

Pull-up and pull-down networks are duals.

To design one gate, first design one network, then compute dual to get other network.

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Static CMOS Circuits

Static CMOS Logic Structure Logic Gates – Inverter, NAND and NOR Complex Structures AOI/OAI Structures Stick Diagrams Layouts

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Inverter

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NAND Gate

Va Vb Vout

0 0

0 1

1 0

1 1

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NOR2 Gate

Va Vb Vout

0 0

0 1

1 0

1 1

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Static CMOS Circuits

Static CMOS Logic Structure Logic Gates – Inverter, NAND and NOR Complex Structures AOI/OAI Structures Stick Diagrams Layouts

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Complex CMOS Structures

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Xor gate

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Static CMOS Circuits

Static CMOS Logic Structure Logic Gates – Inverter, NAND and NOR Complex Structures AOI/OAI Structures Stick Diagrams Layouts

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AOI/OAI gates

AOI = and/or/invert; OAI = or/and/invert. Implement larger functions. Pull-up and pull-down networks are compact:

smaller area, higher speed than NAND/NOR network equivalents.

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AOI example

and

or

invert

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Problems

A

A

B

C

C

B

D

D

Y

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Problems

Design a CMOS circuit to implement the logic Y = A'B' + B'C + C'A

Make a 2 input CMOS XOR gate to implement Y = A B.

CMOS XOR and XNOR gates are similar. Just one of the input pairs (A and A' are reversed).

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Static CMOS Circuits

Static CMOS Logic Structure Logic Gates – Inverter, NAND and NOR Complex Structures AOI/OAI Structures Stick Diagrams Layouts

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Stick diagrams

A stick diagram is a cartoon 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.

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Stick Diagram of NOR gate

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Dynamic latch

Stores charge on inverter gate capacitance:

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Dynamic latch stick diagram

VDD

in

VSSphiphi’

out

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Static CMOS Circuits

Static CMOS Logic Structure Logic Gates – Inverter, NAND and NOR Complex Structures AOI/OAI Structures Stick Diagrams Layouts

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Layout

D Q’

VDD

VSS

’

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Layout of NOR Gate

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Stick Diagram of NAND gate