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240-451 VLSI lecture, 2000 Lecture 4 MOS Circuits Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Combination & Sequential

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Combination & Sequential

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut CMOS logic style

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Example NAND gate

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut 4-input NAND gate

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Example : NOR gate

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Complex CMOS gate

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Complex gate structures A C B A B C Vdd Gnd Out Out = A+(B*C)... A B C And-Or-Invert (AOI) How to add terms?

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut A C B A B C Vdd Gnd Out Out = A+(B*C)... A B C And-Or-Invert (AOI) How to add terms? OAI/AOI duality

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Demorgans law in action Out = A*(B+C)... A B C Or-And-Invert (OAI) A C B A B C Vdd Gnd Out

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Demorgans law in action Out = A*(B+C)... A B C Or-And-Invert (OAI) A C B A B C Vdd Gnd Out

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Demorgans law in action Out = A*(B+C)... A B C Or-And-Invert (OAI) A C B A B C Vdd Gnd Out

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Demorgans law in action Out = A*(B+C)... A B C Or-And-Invert (OAI) A C B A B C Vdd Gnd Out

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Demorgans law in action Out = A*(B+C)... A B C Or-And-Invert (OAI) A C B A B C Vdd Gnd Out What is the Magic command to do this?

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut OAI/AOI duality A C B A B C Vdd Gnd Out A C B A B C Vdd Gnd Out

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Step by step layout XNOR gate The equation for XNOR is: –f = (a * b) + (a' * b') using DeMorgan's law on each of the two terms gives: –f = (a'+ b')' + (a + b)' using DeMorgan's law on the two terms together gives: –f = ((a'+ b') * (a + b))' This could be directly implemented with a single complementary CMOS gate: the equation is in a simple negated product of sums form. This form can be implemented with the standard Or-And-Invert (OAI) style gate.

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Non-inverter input However, using DeMorgan's law one more time on the left term gives: –f = ((a * b)' * (a + b)) This form uses no inverted inputs and can be implemented with two gates a NAND gate and an OAI gate. a b f

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Logic Graph

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Example CMOS

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240-451 VLSI lecture, 2000 Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut Complex CMOS graph

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Chapter 3 Digital Logic Structures

Chapter 3 Digital Logic Structures

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