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Important Digital Logic and Design Short Questions

Chapter: 17
Question 1:
What happens when the D input is 0 in a 4-to-16 Decoder using two 3-to-8 Decoders?
Answer: When the D input is 0, the upper decoder is selected. The A, B, and C inputs select the appropriate output of the upper decoder.
Chapter: 17
Question 2:
How can the 74XX138 Decoder be used to implement a Boolean expression in POS form?
Answer: The 74XX138 Decoder can implement a POS Boolean expression by using an AND gate to combine the outputs corresponding to the sum terms in the Karnaugh Map.
Chapter: 17
Question 3:
What does a BCD to 7-Segment Decoder do?
Answer: A BCD to 7-Segment Decoder converts a 4-bit BCD code into a 7-segment code, activating a unique set of outputs for each BCD input.
Chapter: 17
Question 4:
What is the MSI 7-Segment Decoder IC, and what are its key features?
Answer: The MSI 7-Segment Decoder IC is the 74LS47, which has 4-bit BCD input and 7-bit active-low outputs. It also includes LT, RBI, and BI/RBO inputs for testing.
Chapter: 17
Question 5:
What is the difference between a BCD-to-Decimal Decoder and a Binary 4-to-16 Decoder?
Answer: A BCD-to-Decimal Decoder has ten outputs for valid BCD inputs (0-9), while a Binary 4-to-16 Decoder has sixteen outputs for all 4-bit binary combinations.
Chapter: 17
Question 6:
How does an Encoder differ from a Decoder?
Answer: An Encoder performs the opposite function of a Decoder, generating a binary output representing the selected input from multiple active inputs.
Chapter: 17
Question 7:
What is the function of a Priority Encoder?
Answer: A Priority Encoder outputs the binary code of the highest-priority active input, resolving conflicts when multiple inputs are active simultaneously.
Chapter: 17
Question 8:
How does a Multiplexer operate in a digital circuit?
Answer: A Multiplexer selects one of several input signals and routes it to a single output, often used in ALUs to select data from different registers for operations.
Chapter: 17
Question 9:
What is the purpose of the LT input in the 7-Segment Decoder IC?
Answer: The LT (Lamp Test) input is used to turn on all segments of the 7-segment display to check that no segments are burned out.
Chapter: 17
Question 10:
What problem is solved by using a Priority Encoder instead of a simple Binary Encoder?
Answer: A Priority Encoder resolves conflicts by ensuring that the highest-priority input is encoded when multiple inputs are active simultaneously.