Deck 3: Describing Logic Circuits

Question 1

A ___________is used to illustrate the various input/output combinations for a logic gate.

A) logic function diagram
B) Boolean formula
C) Boolean diagram
D) truth table

Answer 1

truth table

Question 2

Boolean variables are allowed to have how many possible values?

A) any number
B) two
C) none
D) one

Answer 2

two

Question 3

Which of the following is NOT a basic Boolean operation?

A) NOT
B) AND
C) OR
D) FOR

Answer 3

FOR

Question 4

Which logic function provides a low output in response to one or more low inputs?

A) AND
B) OR
C) FOR
D) NOT

Question 5

Which logic function provides a low output only when all inputs are low?

A) NOT
B) FOR
C) AND
D) OR

Question 6

How many truth table entries are required for a four- input circuit?

A) 8
B) 4
C) 12
D) 16

Question 7

The truth table shown below describes a(n)___________gate.

A) AND
B) NAND
C) XOR
D) XNOR

Question 8

A certain printer requires that all of the following conditions be satisfied before it will send a HIGH to a microprocessor acknowledging that it is ready to print: 1. The printer's electronic circuits must be energized.
2. Paper must be loaded and ready to advance.
3. The printer must be "on line" with the microprocessor.
As each of the above conditions is satisfied, a HIGH is generated and applied to a 3- input logic gate. When all three conditions are met, the logic gate produces a HIGH output indicating readiness to print. The basic logic gate used in this circuit would be a(n):

A) OR gate.
B) AND gate.
C) NOR gate.
D) NOT gate.

Question 9

In Boolean algebra, the commutative laws indicate that:

A) the factoring of Boolean expressions requires the multiplication of product terms that contain like variables.
B) the order in which we OR or AND two variables does not affect the result.
C) an expression can be expanded by multiplying term by term just the same as in ordinary algebra.
D) we can group variables in an AND or in an OR expression any way we want.

Question 10

The logic gate that generates a HIGH (1) output when any one of its inputs is HIGH is the:

A) OR gate.
B) NOR gate.
C) NOT operation.
D) AND gate.

Question 11

The logic gate that generates a HIGH (1) output only when all of its inputs are LOW (0) is the:

A) NAND gate.
B) NOR gate.
C) OR gate.
D) AND gate.

Question 12

Two signals (A and B) are ORed. Their product is then ANDed with signals C and D. Which of the following expressions describes this series of operations?

A) (A + B) CD
B) A + BCD
C) A + B(CD)
D) A + (B + CD)

Question 13

Which of the following statements best describes the function of the logic variable X?

A) X is a variable whose value is always 1.
B) X is a variable whose value is 1 or 0.
C) X is a constant value in the indeterminate range of logic values.
D) X is a variable whose value is always 0.

Question 14

Which of the following logical operations is represented by the + sign in Boolean algebra?

A) Inversion
B) AND
C) OR
D) Complementation

Question 15

The Boolean expression X = is logically equivalent to what single gate?

A) OR gate
B) NAND gate
C) NOR gate
D) AND gate

Question 16

Which of the following gates is the output gate for a circuit with the expression Y = ?

A) NAND
B) AND
C) OR
D) NOR

Question 17

Given the Boolean expression X = and the values L = 1, M = 0, N = 1, D = 1, and G = 0, the value of X is:

A) 1
B) 0

Question 18

The output of a three input (A, B, and C) AND gate is connected to a two input OR gate. A second input to the OR gate is labeled D. The Boolean expression representing this logic circuit is:

A) X = ABC + D
B) X = (A + B + C) + D
C) X = (ABC)D
D) X = (A + B + C) D

Question 19

The alternate logic symbol for an AND gate would have:

A) bubbles only on its output.
B) bubbles only on its inputs.
C) no bubbles on its inputs or outputs.
D) bubbles on its inputs and outputs.

Question 20

A logic control system in an automobile generates an audible alarm when any one, two, or three of the following three conditions occur: 1. The ignition is off but the ignition key has not been removed from the switch and a door is opened.
2. The headlamp switch is on with the ignition off and the key removed from the switch.
3. The ignition is on with the engine running but the driver's seatbelt has not been fastened.
Detection circuits generate HIGH inputs to a 3- input logic gate when any of these conditions occurs. The logic gate responds to the high input(s) by generating a HIGH output that triggers the alarm. The 3- input logic gate is most likely a(n):

A) OR gate.
B) NOR gate.
C) Inversion device.
D) AND gate.

Question 21

Which of the following Boolean relationships is TRUE

A)
B) AB =
C)
D)

Question 22

Suppose that a logic gate has 3 inputs. How many possible input combinations must be listed in its accompanying truth table?

A) 2₁₀
B) 4₁₀
C) 8₁₀
D) 16₁₀

Question 23

Which of the following accurately describes the logic circuit for the Boolean expression AB + BCD?

A) A 2- input NAND gate and 3- input NAND gate whose outputs are fed to a 2- input OR gate.
B) A 2- input AND gate and a 3- input AND gate whose outputs are fed to a 2- input NOR gate.
C) A 2- input OR gate and a 3- input OR gate whose outputs are fed to a 2- input AND gate.
D) A 2- input NOR gate and a 3- input NOR gate whose outputs are fed to a 2- input AND gate.

Question 24

In digital electronics, each of the two normal states of a voltage variable is called a(n):

A) indeterminate value.
B) algebraic sum.
C) actual number.
D) logic level.

Question 25

One of DeMorgan's theorems states that Simply stated, this means that logically there is no difference between:

A) a NOR gate and a NAND gate with inverted inputs.
B) a NOR gate and an AND gate with inverted inputs.
C) an AND gate and a NOR gate with inverted inputs.
D) a NAND gate and an OR gate with inverted inputs.

Question 26

One of DeMorgan's theorems states that = X' + Y'. Simply stated, this means that logically there is no difference between:

A) a NAND gate and an OR gate with inverted inputs.
B) a NOR gate and a NAND gate with inverted inputs.
C) a NOR gate and an AND gate with inverted inputs.
D) an AND gate and a NOR gate with inverted inputs.

Question 27

Which of the following equations would accurately describe a 4- input OR gate when A = 1, B = 1, C = 0, and D = 0?

A) 1 + 1 + 0 + 0 = 00
B) 1 + 1 + 0 + 0 = 01
C) 1 + 1 + 0 + 0 = 0
D) 1 + 1 + 0 + 0 = 1

Question 28

Which of the following groups of logic devices would be required to implement the expression X =?

A) three 3- input AND gates, one 3- input OR gate, and two inverters
B) two 3- input AND gates, two 3- input OR gates, and three inverters
C) two 3- input AND gates, one 2- input AND gate, one 3- input OR gate, and two inverters
D) three 3- input AND gates, two 3- input OR gates, and two inverters

Question 29

A NAND gate has:

A) active high inputs and an active low output.
B) active low inputs and an active high output.
C) active high inputs and an active high output.
D) active low inputs and an active low output.

Question 30

The basic logic device that always has a single input is the:

A) OR gate.
B) AND gate.
C) Comparator.
D) Inverter.

Question 31

Logically, the output of a NOR gate would have the same Boolean expression as a(n):

A) NAND gate immediately followed by an inverter.
B) AND gate immediately followed by an inverter.
C) NOR gate immediately followed by an inverter.
D) OR gate immediately followed by an inverter.

Question 32

If you apply DeMorgan's theorem to the expression you get:

A)
B)
C)
D)

Question 33

The logic circuit whose output is always the inverse of its inputs is the:

A) AND gate.
B) OR gate.
C) Comparator.
D) Inverter.

Question 34

A small circle on the output of a logic gate is used to represent the:

A) AND operation.
B) OR operation.
C) Comparator operation.
D) NOT operation.

Question 35

Which of the following logic devices can be used to implement any Boolean expression?

A) Inverters and AND gates
B) NAND gates and NOR gates
C) Inverters and OR gates
D) AND and OR gates

Question 36

The basic logic gate that must have all of its inputs HIGH to have a high output is the:

A) AND gate.
B) NOT gate.
C) OR gate.
D) NOR gate.

Question 37

The basic logic circuit whose output is the complement of the input is the:

A) Inverter.
B) OR gate.
C) Comparator.
D) AND gate.

Question 38

Which of the following Boolean expressions represents a four input AND gate followed by an inverter?

A) X =
B) X =
C)
D)

Question 39

Select the Boolean expression that is the logical equivalent to the expression .

A) ABC
B)
C) A + B + C
D)

Question 40

How many NAND gates would be required to perform the OR operation if two inputs are required?

A) two
B) one
C) four
D) three

Question 41

If you apply DeMorgan's theorem to the expression you get:

A)
B)
C)
D)

Question 42

The basic logic circuit whose output equals the Boolean algebraic sum of its input is the:

A) Inverter.
B) AND gate.
C) OR gate.
D) Comparator.

Question 43

Which of the following gates generates the exact inverse output of the OR gate for all possible input combinations?

A) NOT
B) NOR
C) NAND
D) AND

Question 44

Which of the three basic logic functions is accomplished by connecting all the inputs of a NAND gate to a single logic function?

A) Inversion
B) AND
C) OR
D) Comparison

Question 45

Which of the following Boolean expressions represents a three input AND gate?

A) X = AB + C
B) X =
C) X = ABC
D) X = A + B + C

Question 46

A certain logic gate has three inputs. The output goes LOW (0) only when the inputs are A = 1, B =

A) AND gate.
B) NOR gate.
C) NAND gate.
D) none of the above

Question 47

The logic gate that generates a LOW (0) output when any one of its inputs are HIGH (1) is the:

A) NOR gate.
B) OR gate.
C) NAND gate.
D) AND gate.

Question 48

74LS00 is a:

A) Quad 2- input AND gate.
B) Quad 2- input OR gate.
C) Single 8- input OR gate.
D) Quad 2- input NAND gate.

Question 49

Often times, an IC input label will contain an over- bar. In order for that particular input to perform a required function:

A) the input needs to be low.
B) the input is active only on PGT.
C) the input is active only on NGT.
D) the input needs to be high.

Question 50

-If we use DeMorgan's theorem to simplify the output expression for the circuit in Figure 3-1, we get:

A)
B) Y = AB +
C) Y =
D) Y =

Question 51

-Refer to Figure 3-1. The output (Y) can be expressed as:

A) Y =
B) Y =
C) Y =
D) Y =

Question 52

-Refer to Figure 3- 1. If A = 1, B = 1, and C = 0, the output (Y) will be:

A) floating.
B) LOW.
C) invalid.
D) HIGH.

Question 53

In the expression X =, one must remember to invert each value before combining values.

Question 54

In an expression containing both AND and OR operations, the AND operations are performed first.

Question 55

A good rule of thumb for logic circuit schematics is to connect bubble outputs to nonbubble inputs whenever possible.

Question 56

Parentheses are used in Boolean expressions to eliminate confusion as to which operation is to be performed first.

Question 57

The output generated by a logic circuit for some combination of inputs can often be determined without using its Boolean expression.

Question 58

The output of a NAND gate is the inverse of the output for an AND gate for all possible input combinations.

Question 59

A minimum of three 2- input NOR gates would be required to perform the logical operation of a single 2- input AND gate.

Question 60

Boolean algebra involves linear and nonlinear equations.

Question 61

The output from a logic gate changes at the same instant that the input to the gate changes.

Question 62

Boolean algebra often results in reduction of electronic circuitry.

Question 63

AND, OR, and NOT gates provide the three primary logic functions.

Question 64

Inverters perform the same functions in a logic circuit regardless whether they are connected to the input or output.

Question 65

OR gates can have more than two inputs.

Question 66

Any logic expression can be implemented using NAND gates.

Question 67

Any logic expression can be implemented using NOR gates.

Question 68

To change a logic gate to its alternate representation, a simple three- step process is followed.

Question 69

Bubbles represent inversion.

Question 70

The terms negate, invert, and NOT describe the same Boolean algebra operation.

Question 71

-Refer to Figure 3- 2. The output (Y) will be HIGH when both A and B are LOW, and C is HIGH.

Question 72

-Refer to Figure 3- 2. The output (Y) will be HIGH whenever A is LOW, and B and C inputs are HIGH.

Question 73

-Refer to Figure 3- 2. The output (Y) will be LOW whenever A and B are HIGH, and C is LOW.

Question 74

The output expression for the circuit in Figure 3- 2 is Y =

Question 75

The voltage ranges used to represent binary 0 and 1 are referred to as_______levels.

Question 76

Basic operations in Boolean algebra are called_______operations.

Question 77

A_______table illustrates the relationship between a logic circuit's output and every possible combination of inputs.

Question 78

In digital applications, a random, brief change in voltage is commonly referred to as a_______
.

Question 79

A tennis player is waiting to receive a serve from their opponent. The opponent hits the
ball to the outside of the service court. The time it takes for the player to process the visual information and then begin to move in the direction of the serve is an example of _______.

Question 80

An active signal applied to a control input is used to _______the circuit.