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Static CMOS Circuits

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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 VDD pull-up network out inputs Pull-down network VSS 7

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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. 13

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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 8

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NAND Gate Va Vb Vout 1

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NOR2 Gate Va Vb Vout 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. 11

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AOI example invert or and 12

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Problems A C B D Y A B C D

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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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**Stores charge on inverter gate capacitance:**

Dynamic latch Stores charge on inverter gate capacitance:

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**Dynamic latch stick diagram**

VDD in out VSS phi phi’

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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 VDD D Q’ VSS f f’

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Layout of NOR Gate

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**Stick Diagram of NAND gate**

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