Chapter 3: Digital Logic Structures

Question 1

MOS Transistors

Answer 1

(metal-oxide semiconductor)
Makes or breaks a closed circuit
Two-Types:
p-type
n-type
Both operate logically (i.e. like switches)

Question 2

3 Terminals of a MOS Transistor

Answer 2

gate
source
drain

Question 3

n-type transistor
Closed circuit if _______
Open circuit if _______

Answer 3

Closed: some amount of voltage (i.e. 2.9 volts)
Open: 0 volts

Question 4

p-type transistor
Closed circuit if _______
Open circuit if _______

Answer 4

Opposite (i.e. complementary) to n-type transistor
Closed: 0 volts
Open: some amount of voltage (i.e. 2.9 volts)

Question 5

CMOS circuits

Answer 5

contain both n-type and p-type transistors

Complementary Metal-Oxide Semiconductor

Question 6

NOT gate

Answer 6

aka “Inverter”

an electronic circuit that implements the NOT logic function.

Question 7

NOR gate

Answer 7

an electronic circuit that implements the NOT-OR logic function.
(exactly the opposite of the OR function)

Question 8

OR gate

Answer 8

an electronic circuit that implements the OR logic function.

achieved by adding an inverter (NOT gate) to a NOR gate.

Question 9

AND gate

Answer 9

an electronic circuit that implements the AND logic function.
achieved by adding an inverter (NOT gate) to a NAND gate.

Question 10

NAND gate

Answer 10

an electronic circuit that implements the NOT-AND logic function.

Question 11

DeMorgan’s Law

Answer 11

“it is not the case that both A and B are false” is equivalent to “at least one of A and B is true”

(see paper note-card for symbolic representation)

Question 12

An n-input AND gate has an output value of 1 only if ____ n input variables have values of __.

Answer 12

ALL

1

Question 13

An n-input OR gate has an output value of 1 if ____ of the n input variables has a value of __.

Answer 13

ANY

1

Question 14

An n-input OR gate has an output value of 0 only if ____ n input variables have values of __.

Answer 14

ALL

0

Question 15

An n-input AND gate has an output value of 0 if ____ of the n input variables has a value of __.

Answer 15

ANY

0

Question 16

Two kinds of logic structures:

Answer 16

1) store information

2) do not store information

Question 17

Decision Elements

Answer 17

aka: combinational logic structures
Logic structures that do not store information.
Outputs are strictly dependent on the combination of input values that are being applied to the structure right now.
Not at all dependent on any past history of information that is stored internally, since no info can be stored internally in this type of circuit.
(e.g. Decoder, Mux, Full Adder)

Question 18

Decoder

Answer 18

exactly one output is 1 and all the rest are 0s.

In general: has n inputs and 2^n outputs.

Question 19

In a Decoder, the output line that detects the the input pattern (i.e. the line that has an output of 1) is _______.

Answer 19

asserted

Question 20

Mux

Answer 20

two-input multiplexer
Function is to select one of the inputs and connect it to the output.
In general: consists of 2^n inputs and n select lines.

Question 21

The Select Signal in a Mux determines ________

Answer 21

which input is connected to the output.
i.e. if S = 0, that input is NOT connected to the output in the example on p.61., if S = 1 then that input IS connected to the output.

Question 22

Full Adder

Answer 22

A logic circuit that provides 3 inputs and 2 outputs

Question 23

Programmable Logic Array (PLA)

Answer 23

an array of AND gates followed by an array of OR gates.
The number of AND gates corresponds to the number of input combinations (rows) in the truth table.
The number of OR gates corresponds to the number of output columns.

Question 24

Logical Completeness

Answer 24

Any logic function can be accomplished as long as there are enough AND, OR, and NOT gates available.
(i.e. the set of gates {AND, OR, NOT} is logically complete because sufficient to build a logic circuit for any truth table)