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WalesElectronicsQuick questions

Component 1: Logic Systems

Quick questions on Logic gates and Boolean algebra: truth tables and De Morgan - WJEC A-Level Electronics

9short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is the laws of Boolean algebra?
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These laws, together with the commutative, associative and distributive rules, let you simplify an expression algebraically. Simplifying matters because fewer gates means a cheaper, faster, lower-power circuit.
What are de Morgan's theorems?
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Misapplying De Morgan. When you break the bar you must change the operator and invert every variable, not just remove the bar.
What is aND?
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output high only when all inputs are high, Q=A⋅BQ = A \cdot B.
What is oR?
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output high when any input is high, Q=A+BQ = A + B.
What is nAND?
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inverted AND, Q=A⋅B‾Q = \overline{A \cdot B}.
What is nOR?
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inverted OR, Q=A+B‾Q = \overline{A + B}.
What is xNOR?
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output high when inputs are the same, Q=A⊕B‾Q = \overline{A \oplus B}.
What is q1?
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Write the truth table for a two-input NOR gate. [2 marks]
What is q2?
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Use De Morgan's theorem to rewrite A+B+C‾\overline{A + B + C} without the long bar. [2 marks]

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