Abhishek Bhattacharjee Topics: square6 Transistors square6 Logic Gates square6 Combinational Circuits square6 Karnaugh Maps Reading: square6 Chapter 4: Section 4.2 CS 211: Computer Architecture Digital Logic
Rutgers University Abhishek Bhattacharjee 2 Transistor: Building Block of Computers Microprocessors contain millions (billions) of transistors square6 Intel Pentium 4 (2000): 48 million square6 IBM PowerPC 750FX (2002): 38 million square6 IBM/Apple PowerPC G5 (2003): 58 million Logically, each transistor acts as a switch Combined to implement logic functions square6 AND, OR, NOT Combined to build higher-level structures square6 Adder, multiplexer, decoder, register, … Combined to build processor
Rutgers University Abhishek Bhattacharjee 3 Simple Switch Circuit Switch open : square6 No current through circuit square6 Light is off square6 V out is +2.9V Switch closed : square6 Current flows square6 Light is on square6 V out is 0V Switch-based circuits can easily represent two states: on/off, open/closed, voltage/no voltage.
Rutgers University Abhishek Bhattacharjee 4 n-type MOS Transistor MOS = Metal Oxide Semiconductor square6 two types: n-type and p-type n-type square6 when Gate has positive voltage, short circuit between #1 and #2 square6 when Gate has zero voltage, open circuit between #1 and #2 Gate = 1 Gate = 0
Rutgers University Abhishek Bhattacharjee 5 p-type MOS Transistor p-type is complementary to n-type square6 when Gate has positive voltage, open circuit between #1 and #2 square6 when Gate has zero voltage, short circuit between #1 and #2 Gate = 1 Gate = 0 Gate = 0
Rutgers University Abhishek Bhattacharjee 6 Logic Gates Use transistors to implement logical functions: AND, OR, NOT Digital symbols: square6 recall that we assign a range of analog voltages to each digital (logic) symbol square6 assignment of voltage ranges depends on electrical properties of transistors being used circle6 typical values for "1": +5V, +3.3V, +2.9V circle6 from now on we'll use +2.9V
Rutgers University Abhishek Bhattacharjee 7 CMOS Circuit Complementary MOS Uses both n-type and p-type MOS transistors square6 p-type circle6
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- Fall '08
- Logic gate, Rutgers University, Abhishek Bhattacharjee