Two 4-bit binary numbers (1011 and 1111) are applied to a 4-bit parallel adder.

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Question
Two 4-bit binary numbers (1011 and 1111) are applied to a 4-bit parallel adder. The carry input is 1. What are the values for the sum and carry output?
Options
A. ∑₄∑₃∑₂∑₁ = 0111, C_out = 0
B. ∑₄∑₃∑₂∑₁ = 1111, C_out = 1
C. ∑₄∑₃∑₂∑₁ = 1011, C_out = 1
D. ∑₄∑₃∑₂∑₁ = 1100, C_out = 1

Correct Answer

∑₄∑₃∑₂∑₁ = 1011, C_out = 1

Combinational Logic Circuits problems

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2. An output gate is connected to four input gates; the circuit does not function. Preliminary tests with the DMM indicate that the power is applied; scope tests show that the primary input gate has a pulsing signal, while the interconnecting node has no signal. The four load gates are all on different ICs. Which instrument will best help isolate the problem?
Options
A. Current tracer
B. Logic probe
C. Oscilloscope
D. Logic analyzer

3. Which of the following combinations of logic gates can decode binary 1101?
Options
A. One 4-input AND gate
B. One 4-input AND gate, one OR gate
C. One 4-input NAND gate, one inverter
D. One 4-input AND gate, one inverter

4. A decoder can be used as a demultiplexer by ________.
Options
A. tying all enable pins LOW
B. tying all data-select lines LOW
C. tying all data-select lines HIGH
D. using the input lines for data selection and an enable line for data input

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