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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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Presentation on theme: "240-451 VLSI lecture, 2000 Lecture 4 MOS Circuits Department of Computer Engineering, Prince of Songkla University by Wannarat Suntiamorntut."— Presentation transcript:

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

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

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

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

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

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

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

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

9 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?

10 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

11 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

12 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

13 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

14 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

15 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?

16 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

17 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.

18 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

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

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

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


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