Logic Gates Flashcards
Gate
A device that performs a basic operation on electrical signals and consists of transistors
Circuits
Gates combined to perform more complicated tasks
What is a transistor?
- semiconductor devise for amplifying, controlling, and generating electrical signals.
Two main roles of a transistor?
Amplify or switch electrical signals and power.
NOT Gate Inputs and Outputs?
- Accepts one input signal and returns the opposite of what was inputted
NOT Gate Boolean Expression
X= A’ and X=NOT(A)
AND Gate Input and Output?
- Accepts two output signals
- If both are 1=1, otherwise the output is 0
AND Gate Boolean and Excel Expression
X= A . B and X = AND(A,B)
OR Gate Input and Outputs
- Accepts two signals
- If both 0=0, otherwise, the output is 1
OR Gate Boolean and Excel Expression
X =A+B and X = OR(A,B)
NAND Gate Input and Output
Combination of NOT and AND
- Accepts two signals
- If both are 1=1, otherwise output is 0
NAND Gate Boolean and Excel Expression
(A . B )’ and X= NOT(OR(A,B))
XOR Gate Input and Output
- Accepts two inputs
- If both are the same, the output is 0, otherwise they are the same
XOR Gate Boolean and Excel Expression
-They are special circuits that carry out additional operations
What is a Half-Adder?
- A circuit that computes the sum of two bits and produces the correct carry bit
- Has two inputs and produces two outputs (sum and carry-in)
What is a Full-Adder?
- A circuit that computes the sum of two bits and a carry bit and produces the correct carry bit
- Has three inputs (A, B, carry-in) and two outputs (sum and carry)
What are some limitations of transistor gates?
- Power is consumed even if nothing is
connected to the output
What are other transistor-based circuits?
-CMOS is much better because power used only during switching from one state to another
What kind of transistors do modern computers use?
-CMOS logic circuits
Why do we need to use transistors?
- Be able to implement the logic functions in hardware
- Perform complex operations
- Power-efficient and can be very fast
- Transistors are building blocks for modern computer microchips
