Which of the following is a characteristic of combinational circuits?
Answer: B
Combinational circuits have outputs that depend solely on the current input values, with no memory or feedback elements involved.
Q.22Hard
A full adder can be implemented using how many NAND gates minimum?
Answer: C
A full adder requires 9 NAND gates minimum when implemented using NAND gates exclusively to realize the sum and carry outputs.
Q.23Easy
In the 2024-25 examination pattern, which logic family provides the lowest power consumption?
Answer: C
CMOS (Complementary Metal-Oxide-Semiconductor) logic has the lowest power consumption, making it the preferred choice for modern digital systems and portable devices.
Q.24Medium
A 3-to-8 decoder with active-low outputs has how many output lines at logic 0 when the input is 101?
Answer: C
A 3-to-8 decoder with active-low outputs means all lines are 1 except the selected one. Input 101 (5 in decimal) selects line 5, so 7 lines remain at 0.
Q.25Medium
In a Priority encoder, when multiple inputs are high simultaneously, which input gets priority?
Answer: C
Priority encoders can be designed with either highest or lowest priority encoding based on the application requirements specified in the design.
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Q.26Easy
The setup time of a flip-flop is defined as:
Answer: B
Setup time is the minimum duration the input data must remain stable and valid before the active clock edge for reliable operation.
Q.27Easy
In a Karnaugh map, what does a larger group of adjacent 1's represent?
Answer: B
Larger groups in K-maps represent simplification with fewer variables in the resulting Boolean expression, reducing circuit complexity.
Q.28Medium
A synchronous BCD counter counts from 0000 to 1001, then resets to 0000. This requires modification of a standard 4-bit counter using:
Answer: B
BCD counters use AND gates to detect when the count reaches 1010 (10 in decimal), triggering a reset to 0000 to maintain BCD counting.
Q.29Medium
Which Boolean algebra theorem states that A + A·B = A?
Answer: A
The Absorption theorem simplifies expressions of the form A + A·B to just A, eliminating redundant terms.
Q.30Easy
In a multiplexer, the number of select lines required to select from 16 data inputs is:
Answer: B
For 2^n data inputs, n select lines are needed. 2^4 = 16, so 4 select lines are required for a 16-to-1 multiplexer.
Q.31Medium
The propagation delay in a synchronous counter is:
Answer: A
In synchronous counters, all flip-flops receive the same clock pulse simultaneously, so propagation delay equals one flip-flop delay, not cumulative.
Q.32Easy
Which of the following is used to convert analog signals to digital for processing?
Answer: C
ADCs are specifically designed to convert continuous analog signals into discrete digital representations for digital processing systems.
Q.33Medium
In Quine-McCluskey method, prime implicants are:
Answer: B
Prime implicants are maximal groups of 1's that cannot be combined with other groups, representing the simplest possible terms.
Q.34Easy
A JK flip-flop with J=1, K=1 and clock pulse will:
Answer: C
When both J and K inputs are 1 in a JK flip-flop, the output toggles on the clock pulse, changing from 0 to 1 or 1 to 0.
Q.35Medium
The hold time specification for a flip-flop ensures that:
Answer: A
Hold time is the minimum duration data must remain stable after the clock edge to ensure reliable capture and operation.
Q.36Medium
In a 8-bit parallel-in serial-out (PISO) shift register, how many clock pulses are needed to output all data?
Answer: B
To shift out 8 bits of data serially, 8 clock pulses are required, one for each bit output.
Q.37Medium
Which characteristic distinguishes CMOS gates from TTL gates in practical applications?
Answer: C
CMOS gates consume minimal static power (only during transitions), making them ideal for battery-operated and portable applications.
Q.38Hard
In a Gray code counter, consecutive counts differ by exactly:
Answer: A
Gray code is designed such that consecutive values differ in exactly one bit position, reducing transition errors in digital systems.
Q.39Easy
In a 4-to-1 multiplexer, how many select lines are required?
Answer: B
For a 4-to-1 multiplexer, we need log₂(4) = 2 select lines to choose one of 4 input lines.
Q.40Easy
What is the output of an SR flip-flop when S=1 and R=1 (NOR gate implementation)?
Answer: C
When both S=1 and R=1 in NOR-based SR flip-flop, both outputs become 0, which violates the Q and Q' complementary property, making it an invalid state.
