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Subel. E
6 questions
Subelement E
Digital Logic
Section 35
Logic Levels
In a negative-logic circuit, what level is used to represent a logic 0?
  • Low level.
  • Positive-transition level.
  • Negative-transition level.
  • Correct Answer
    High level.

In a negative-logic circuit, what level is used to represent a logic 0?

High level.

In positive logic, 1 is high level while 0 is low. But, in negative logic it is reversed, with 1 being low, and 0 being high. Analysis of logic circuits starts with the assumption on whether it is a positive or negative logic.

See the Electrical And Electronics Portal site for the article Definition of Logic Gates | Positive and Negative Logic | Truth table | Types of Logic Gates

Also, see the EEtimes site for the article on Logic 101 – Part 2 – Positive vs Negative Logic

And, see the Tutorial Cup site for the article Positive and Negative logic in Digital Electronics Basic difference between positive and negative logic

See Wikipedia's article on Logic gate.

For more information, please see the TechTarget site for the article logic gate (AND, OR, XOR, NOT, NAND, NOR and XNOR)

Also, see the Tutorials Point site for the article Logic Gates

Last edited by markadlerdallas. Register to edit

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For the logic input levels shown in Figure 3E12, what are the logic levels of test points A, B and C in this circuit? (Assume positive logic.)
  • A is high, B is low and C is low.
  • Correct Answer
    A is low, B is high and C is high.
  • A is high, B is high and C is low.
  • A is low, B is high and C is low.

For the logic input levels shown in Figure 3E12, what are the logic levels of test points A, B and C in this circuit?
(Assume positive logic.)

A is low, B is high and C is high.

Please notice that the path from either H(igh) is not clear, thus A is low. On the other hand, the opposite is for B, and C is high.

From sammylandler:

The answer to this truth table is found by finding the output of each symbol. Each output will go into the next input. In this problem, each of these truth table symbols are NAND gates.
See Wikipedia's article Truth table a NAND gate is defined as follows:

"The logical NAND is an operation on two logical values, typically the values of two propositions, that produces a value of false if both of its operands are true. In other words, it produces a value of true if at least one of its operands is false."

The L and H values indicate LOW and HIGH logic states.

See Wikipedia's article on Logic gate.

For more information, please see the TechTarget site for the article logic gate (AND, OR, XOR, NOT, NAND, NOR and XNOR)

Also, see the Tutorials Point site for the article Logic Gates

Last edited by markadlerdallas. Register to edit

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For the logic input levels given in Figure 3E13, what are the logic levels of test points A, B and C in this circuit? (Assume positive logic.)
  • A is low, B is low and C is high.
  • A is low, B is high and C is low.
  • Correct Answer
    A is high, B is high and C is high.
  • A is high, B is low and C is low.

For the logic input levels given in Figure 3E13, what are the logic levels of test points A, B and C in this circuit? (Assume positive logic.)

A is high, B is high and C is high.

From sammylandler:

The answer to this truth table is found by finding the output of each symbol. Each output will go into the next input. In this problem, each of these truth table symbols are NAND gates.
See Wikipedia's article Truth table a NAND gate is defined as follows:

"The logical NAND is an operation on two logical values, typically the values of two propositions, that produces a value of false if both of its operands are true. In other words, it produces a value of true if at least one of its operands is false."

The L and H values indicate LOW and HIGH logic states.

See Wikipedia's article on Logic gate.

For more information, please see the TechTarget site for the article logic gate (AND, OR, XOR, NOT, NAND, NOR and XNOR)

Also, see the Tutorials Point site for the article Logic Gates

Last edited by markadlerdallas. Register to edit

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In a positive-logic circuit, what level is used to represent a logic 1?
  • Correct Answer
    High level
  • Low level
  • Positive-transition level
  • Negative-transition level

In a positive-logic circuit, what level is used to represent logic 1?

High level

See Wikipedia's article on Logic gate.

For more information, please see the TechTarget site for the article logic gate (AND, OR, XOR, NOT, NAND, NOR and XNOR)

Also, see the Tutorials Point site for the article Logic Gates

Last edited by markadlerdallas. Register to edit

Tags: none

Given the input levels shown in Figure 3E14 and assuming positive logic devices, what would the output be?
  • Correct Answer
    A is low, B is high and C is high.
  • A is high, B is high and C is low.
  • A is low, B is low and C is high.
  • None of the above are correct.

Given the input levels shown in Figure 3E14 and assuming positive logic devices, what would the output be?

A is low, B is high and C is high.

From sammylandler:

The answer to this truth table is found by finding the output of each symbol. Each output will go into the next input. In this problem, each of these truth table symbols are NAND gates.
See Wikipedia's article Truth table a NAND gate is defined as follows:

"The logical NAND is an operation on two logical values, typically the values of two propositions, that produces a value of false if both of its operands are true. In other words, it produces a value of true if at least one of its operands is false."

The L and H values indicate LOW and HIGH logic states.

See Wikipedia's article on Logic gate.

For more information, please see the TechTarget site for the article logic gate (AND, OR, XOR, NOT, NAND, NOR and XNOR)

Also, see the Tutorials Point site for the article Logic Gates

Last edited by markadlerdallas. Register to edit

Tags: none

What is a truth table?
  • Correct Answer
    A list of input combinations and their corresponding outputs that characterizes a digital device’s function.
  • A table of logic symbols that indicate the high logic states of an op-amp.
  • A diagram showing logic states when the digital device’s output is true.
  • A table of logic symbols that indicates the low logic states of an op-amp.

What is a truth table?

A list of input combinations and their corresponding outputs that characterizes a digital device function.

From kj6prf:

A truth table simply lists all of the possible digital inputs and their corresponding outputs.

For example,
0 0 = 0
0 1 = 0
1 0 = 0
1 1 = 1

is a simple truth table for the AND operation.

See Wikipedia's article on Truth table

For more information, please see the Britannica site for the article truth table

Last edited by markadlerdallas. Register to edit

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