Logic Gates

Digital Signals Logic Gates NOT (Inverter) Gate AND Gate OR Gate NAND Gate NOR Gate XOR Gate

Digital Signals Digital signals 0 (false) or 1 (true) Digital signal 1 is represented by a small voltage. Digital signal 0 is represented by no voltage. Digital Waveforms Each column represents a small amount of time 1 (3V) 0 (0V)

Logic Gates An electronic system that performs a logical operation on an input signal Gates process digital inputs to produce digital outputs. How do computer processors make decisions? How do they do math? Display images? Etc.? LOGIC

1 0 NOT (Inverter) Gate A logic gate that changes its input logic level to the opposite state Symbol 0 1 Truth Table: A table listing all possible inputs to a circuit and the corresponding outputs Truth Table NOT Gate Input (A)Output (Y) A Y

Logic Word Problems If I am hungry and it is 5:00 p.m., then I will eat dinner. If I pedal harder or go downhill, then my bike will go faster. If it is windy and cold, then I am not going to walk home. If my battery is dead or I forget headphones, then I cannot listen to my music. Each word problem uses the same logic as a common gate.

AND Gate If I am hungry AND it is 5:00 p.m., then I will eat dinner. A logic circuit whose: Inputs both = 1 then, Output = 1 Symbol

AND Gate Truth Table AND Gate Input (A)Input (B)Output (Y) A B 0 00 Y

OR Gate If I pedal harder OR go downhill, then my bike will go faster. A logic circuit when: Either Input = 1 then, Output = 1 Symbol

OR Gate Truth Table OR Gate Input (A)Input (B)Output (Y) A B 0 00 Y

NAND Gate If it is windy AND cold, then I am NOT going to walk home. A logic circuit whose: Inputs both = 1 then, Output = 0 Symbol

NAND Gate Truth Table NAND Gate Input (A)Input (B)Output (Y) A B 0 10 Y

NOR Gate If my battery is dead OR I forget headphones, then I will NOT listen to my music. A logic circuit when: Either Input = 1 then, Output = 0 Symbol

NOR Gate Truth Table NOR Gate Input (A)Input (B)Output (Y) A B 0 10 Y

XOR Gate I only have enough money for one friend to go to dinner with me. If either one (but not both) want to go to dinner, well go to dinner. A logic circuit when: If A or B = 1, but not both, then Output = 0 Symbol Possible Inputs (conditions)Outputs First Friend wants to go to dinner (T or F) Second friend wants to go to dinner (T or F) We will go to dinner (T or F) FFF FTT TFT TTF

XOR Gate Truth Table XOR Gate Input (A)Input (B)Output (Y) A B Y

Logic Gates Digital Signals Logic Gates NOT (Inverter) Gate AND Gate OR Gate NAND Gate NOR Gate XOR Gate

Image Resources Microsoft, Inc. (2008). Clip Art. Retrieved September 10, 2008, from