Digital Logic Quiz: Truth Tables and Logic Gates
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Questions and Answers

What is the number of input combinations in a two-input truth table?

  • 16
  • 8
  • 4 (correct)
  • 2

    • What is the purpose of a logic gate?

  • To design electronic circuits
  • To create mechanical devices
  • To implement boolean logic (correct)
  • To implement analog logic

    • What determines the actual values for x in a truth table?

  • The output state
  • The type of logic circuit (correct)
  • The binary counting sequence
  • The number of input combinations

    • What is the general formula for the number of input combinations in an N-input truth table?

    <p>2^N</p> Signup and view all the answers

    What is the purpose of a truth table?

    <p>To list all possible combinations of input logic levels</p> Signup and view all the answers

    What is a logic circuit composed of?

    <p>A combination of logic gates</p> Signup and view all the answers

    How many entries are there in a four-input truth table?

    <p>16</p> Signup and view all the answers

    What is the relationship between the list of all possible input combinations and the binary counting sequence?

    <p>They follow the same sequence</p> Signup and view all the answers

    What is the building block of all logic circuits?

    <p>Logic gates</p> Signup and view all the answers

    What is the outcome of the OR operation when both inputs are 0?

    <p>X is always 0</p> Signup and view all the answers

    What is the Boolean expression for the OR operation?

    <p>X = A + B</p> Signup and view all the answers

    What is the result of combining three inputs using the OR operation, where all three inputs are 1?

    <p>X = 1</p> Signup and view all the answers

    What is the purpose of the OR operation in logic circuits?

    <p>To produce a logic 1 for every combination of input levels where one or more inputs are 1</p> Signup and view all the answers

    What is the difference between the OR operation and ordinary addition in Boolean algebra?

    <p>The OR operation produces 1 + 1 = 1, not 1 + 1 = 2</p> Signup and view all the answers

    What is an example of a complex combination of logic circuits?

    <p>An integrated circuit</p> Signup and view all the answers

    How many basic Boolean operations are learned in digital techniques?

    <p>3</p> Signup and view all the answers

    What is the initial value of the R input in the given latch circuit?

    <p>Logic 1</p> Signup and view all the answers

    What is the output of the upper NAND gate when the inputs are 0 and 1?

    <p>Logic 1</p> Signup and view all the answers

    What is the effect of the output of the lower NAND gate on the upper NAND gate?

    <p>It does not affect the output</p> Signup and view all the answers

    What is the final state of the Q and Q' outputs after the flip-flop has changed?

    <p>Q = 1, Q' = 0</p> Signup and view all the answers

    What is the relationship between the outputs Q and Q' under normal conditions?

    <p>They are the inverse of each other</p> Signup and view all the answers

    What is the sequence of events that causes the flip-flop to change?

    <p>S input goes low, then R input goes high</p> Signup and view all the answers

    What is the role of the R input in the given latch circuit?

    <p>It provides a high signal to the upper NAND gate</p> Signup and view all the answers

    What happens to the outputs Q and Q' when the latch circuit is triggered?

    <p>They flip</p> Signup and view all the answers

    What is the output expression of an inverter in a logic-circuit diagram?

    <p>The input expression with a bar over it</p> Signup and view all the answers

    What is the notation used to represent an inverted value in plain text?

    <p>A_bar</p> Signup and view all the answers

    What is the equation for the circuit on the left in the diagram?

    <p>A_bar + B</p> Signup and view all the answers

    What is the output of the inverter in the right circuit?

    <p>(A + B)_bar</p> Signup and view all the answers

    What is the significance of the bar covering the entire expression in the right circuit?

    <p>It indicates the entire expression is inverted</p> Signup and view all the answers

    What is true about the expressions A + B̄ and A + B?

    <p>They are never equal</p> Signup and view all the answers

    What is the purpose of using an inverter in a logic circuit?

    <p>To invert the input signal</p> Signup and view all the answers

    What is the advantage of using a physical bar over the variable in a logic circuit?

    <p>It makes the circuit easier to read</p> Signup and view all the answers

    What is the primary function of an S-R flip-flop?

    <p>To latch the output to either 1 or 0</p> Signup and view all the answers

    What is the name of the circuit shown in the diagram?

    <p>S-R flip-flop</p> Signup and view all the answers

    What is the meaning of the term 'invalid state' in the context of flip-flops?

    <p>When the flip-flop is in a state of limbo</p> Signup and view all the answers

    What happens when both inputs of an S-R latch are high?

    <p>The latch remains in the last state it was told to switch to</p> Signup and view all the answers

    What type of gate is used to construct the S-R flip-flop in the diagram?

    <p>NAND gate</p> Signup and view all the answers

    What is the purpose of the Q and Q' outputs in an S-R flip-flop?

    <p>To output the current state of the flip-flop</p> Signup and view all the answers

    What is the name of the type of flip-flop that is also known as an S-R latch?

    <p>Set-Reset flip-flop</p> Signup and view all the answers

    What happens when an S-R flip-flop is in an invalid state?

    <p>The flip-flop may switch to reverse the output states or remain in an existing condition</p> Signup and view all the answers

    Study Notes

    Truth Tables

    • A table that lists all possible combinations of input logic levels on the left and the resultant logic level for output x on the right.
    • The number of input combinations will equal 2N for an N-input truth table.
    • The actual values for x will depend on the type of logic circuit.

    Simple Logic Gates

    • A logic gate is an ideal representation of a physical electronic device that implements boolean logic.
    • Logic gates create a logic circuit, which are used in electronic devices, creating integrated circuits and microprocessors.
    • The building block of all logic circuits is the logic gate.
    • All logic actions can be analyzed and simplified into basic actions that are called OR gates, AND gates, and NOT gates.

    OR Gates

    • The OR operation combines two logic inputs, A and B, to produce an output, X.
    • The output is a logic 1 for every combination of input levels where one or more inputs are 1.
    • The boolean expression for the OR operation is X = A + B.

    Inverters in Circuits

    • An inverter (NOT gate) in a logic-circuit diagram has an output expression equal to the input expression with a bar over it.
    • The equation for a circuit using an inverter is A_bar + B, where A_bar is the inverted value of A.

    Flip-Flops

    • A flip-flop is a type of logic circuit that can store a bit (a 0 or 1).
    • Types of flip-flops include Set-Reset (SR) flip-flop, Master-Slave (JK) flip-flop, Data (D) flip-flop, and Toggle (T) flip-flop.
    • An SR flip-flop can be constructed using two NAND gates.

    SR Flip-Flop Operation (NAND)

    • The SR flip-flop has two inputs, S (Set) and R (Reset), and two outputs, Q and Q'.
    • The circuit is also known as an S-R latch, where the outputs "latch" to either 1 or 0 based on a pulsed input.
    • The latch is in an invalid state when both inputs are high.
    • When S is 0 and R is 1, the latch flips, and Q becomes 1 and Q' becomes 0.

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    Test your knowledge of truth tables and simple logic gates, fundamentals of digital logic and electronic devices.

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