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1 Static CMOS Circuits

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Ankur Agarwal 2 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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Ankur Agarwal 3 Static complementary gate structure Pull-up and pull-down networks pull-up network Pull-down network V DD V SS out inputs

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Ankur Agarwal 4 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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Ankur Agarwal 5 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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Ankur Agarwal 6 Inverter

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Ankur Agarwal 7 NAND Gate V a V b V out

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Ankur Agarwal 8 NOR2 Gate V a V b V out

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Ankur Agarwal 9 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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Ankur Agarwal 10 Complex CMOS Structures

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Ankur Agarwal 11 Xor gate

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Ankur Agarwal 12 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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Ankur Agarwal 13 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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Ankur Agarwal 14 AOI example and or invert

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Ankur Agarwal 15 Problems A A B C C B D D Y

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Ankur Agarwal 16 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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Ankur Agarwal 17 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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Ankur Agarwal 18 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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Ankur Agarwal 19 Stick Diagram of NOR gate

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Ankur Agarwal 20 Dynamic latch Stores charge on inverter gate capacitance:

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Ankur Agarwal 21 Dynamic latch stick diagram VDD in VSS phi out

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Ankur Agarwal 22 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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Ankur Agarwal 23 Layout DQ V DD V SS

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Ankur Agarwal 24 Layout of NOR Gate

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Ankur Agarwal 25 Stick Diagram of NAND gate

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