Chapter 4
Gate- A device that performs a basic operation on electrical signals, accepting one or more input signals
and producing a single output signal
Circuits: A combination of interacting gates designed to accomplish a specific logical function
Boolean algebra: A mathematical notation for expressing two-valued logical function
Logic diagram: A graphical representation of a circuit; each type of gate has its own symbol
Truth table: A table showing all possible input values and the associated output values
Six types of gates
NOT AND OR XOR NAND NOR
typically, logic diagrams are black and white with gates distinguished only by their shape
NOT gate- accepts one input signal (0 or 1) and returns the opposite signal as output
AND gate- accepts 2 input signals, If both are 1, the output is 1; otherwise, the output is 0
OR gate -accepts two input signals, If both are 0, the output is 0; otherwise, the output is 1 XOR gate- accepts two input signals, If both are the same, the output is 0; otherwise, the output is 1
NAND gate -accepts two input signals, If both are 1, the output is 0; otherwise, the output is 1
NOR gate- accepts two input signals, If both are 0, the output is 1; otherwise, the output is 0
A NOT gate inverts its single input value
An AND gate produces 1 if both input values are 1
An OR gate produces 0 if both input values are 0 otherwise there all 1
An XOR gate produces 0 if input values are the same, or produces 1 if one or the other inputs are 1
A NAND gate produces 0 if both inputs are 1 (opposite results of a AND gate)
A NOR gate produces a 1 if both inputs are 0 (opposite results of a OR gate)
Gates can be designed to accept three or more input values
Transistor : A device that acts either as a wire that conducts electricity or as a resistor that blocks the
flow of electricity, depending on the voltage level of an input signal. A transistor has no moving parts,
yet acts like
a switch
Semiconductor: ex. Silicon, This is neither a good conductor of electricity nor a good insulator Constructing Gates
A transistor has three terminals
-A source
-A base
-An emitter, typically connected to a ground wire
If the electrical signal is grounded; it is allowed to flow through an
alternative route to the ground (literally) where it ca

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