Gates and circuits

Question 1

What is a gate?

Answer 1

A device that performs a basic operation on

electrical signals, accepting one or more input signals and proucing a single output signle.

Question 2

What is a circuit?

Answer 2

a combination of interacting gates designed to perform a specific logical function.

Question 3

What are the three notations of logic gates, and what are they?

Answer 3

Boolean expressions: Uses Boolean algebra, a mathematical notation for
expressing two-valued logic

Logic diagrams: A graphical representation of a circuit; each gate has its
own symbol

Truth tables: A table showing all possible input values and the associated
output values

Question 4

What are the 6 main gates?

Answer 4

– NOT
– AND
– OR
– XOR
– NAND
– NOR

Question 5

Not gate.

Answer 5

A NOT gate accepts one input signal (0 or 1) and
returns the complementary (opposite) signal as
output.

Question 6

What is a transistor?

Answer 6

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
It is made of a semiconductor material, which is neither a particularly good conductor of electricity nor a particularly good insulator

Question 7

What is a semi-conductor?

Answer 7

Material such as silicon that is neither good at conducting or insulating.

Question 8

What are combinational circuits?

Answer 8

A circuit whose outputs are solely determined by its input values.

Question 9

What is a sequential circuit?

Answer 9

A circuit whose output is a function of its input values and the current state of the circuit.

Question 10

What is circuit equivalence?

Answer 10

The same output for each corresponding input value combination for two circuits.

Question 11

What is an adder?

Answer 11

An electronic circuit that performs an addition operation on binary values.

Question 12

what is a half adder?

Answer 12

A circuit that computes the sum of two bits and produces the appropriate carry bit.

Question 13

What is a full adder?

Answer 13

A circuit that computes the sum of to bits, taking an input carry bit into account.

Question 14

Draw a half adder.

Answer 14

Google it

Question 15

Draw a full adder

Answer 15

Google it

Question 16

Draw a transistor

Answer 16

Google it

Question 17

how does a transistor work?

Answer 17

Takes in a source signal. If this source signal is high (above 5V) then it is grounded, and so the output signal is low (0V). if the source signal is low then it is not pulled towards the ground so the output signal is high. a high output signal represents a 1 and a low represents a 0.

Question 18

what is a not gate made from.

Answer 18

One transistor, and it is essentially the same as the original transistor. if input signal is high then it is grounded, and so output signal is low. and vice versa.

Question 19

What is a NAND gate made from and how does it work?

Answer 19

requires two transistors in series. If both input signals are high the source is grounded and the output signal is therefore low. if either input signal is low, then one transistor keeps the other from being grounded and so the output is high.

Question 20

What is a NOR gate made from and how does it work?

Answer 20

made from two transistors in parallel. The source signal connects to the transistors sepertaly. If either transister allows the wource signal to be grounded, the output is 0.

Question 21

How can an AND or OR gate be constructed.

Answer 21

pass the output of the NAND gate through a NOT gate (essentially just a transister) and this reverses the NOT. This will require 3 transistors - 2 for the NAND and 1 for the NOT.
This also applies the the NOR gate.

Question 22

What is a multiplexer?

Answer 22

it is a general circuit that produces a single output

A circuit that uses a few input control signals to determine which of several input data lines is to be routed too.

Question 23

What is an integrated circuit chip?

What are the sizes?

Answer 23

A piece of silicon on which multiple gates have been embedded.
SSI - Small-Scale integration - 1 to 10
MSI - Medium-Scale integration - 10 to 100
LSI - Large-Scale intergration - 100 to 100,000
VLSI - very large-scale intergration - more than 100,000