Question
What does “positive logic” mean in reference to logic devices?
Answer Options
- A) The logic devices have high noise immunity
- B) High voltage represents a 1, low voltage a 0
- C) The logic circuit is in the “true” condition
- D) 1s and 0s are defined as different positive voltage levels
Correct Answer: B
Explanation
The terms ‘positive logic’ and ‘negative logic’ define the convention used to map the electrical voltage levels in a digital circuit to the abstract binary logic states of ‘1’ (True) and ‘0’ (False). This convention is standardized for virtually all common digital integrated circuits (ICs).
In positive logic, the convention is that a High voltage represents a logic 1, and a low voltage represents a logic 0. For example, in a 5 \text{ V} TTL system, 5 \text{ V} is typically a ‘1’ and 0 \text{ V} is a ‘0’. The opposite, where low voltage is a ‘1’ and high voltage is a ‘0’, is called negative logic.
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