BEE Bachelor of Electrical Engineering Digital Logic and Systems Questions and Answers

Question 1

Which of the following statements accurately describes a key difference between a ripple counter (asynchronous) and a synchronous counter?

Accepted Answer

In a ripple counter, the clock input of subsequent flip-flops is triggered by the output of the preceding flip-flop, while in a synchronous counter, all flip-flops are triggered by a common clock signal.

Answer

Ripple counters are faster and have less propagation delay compared to synchronous counters because they don't have to wait for a common clock pulse.

Answer

Synchronous counters are simpler to design and implement than ripple counters, especially for a large number of bits.

Answer

A ripple counter can count in any desired sequence (up, down, or custom), whereas a synchronous counter is limited to a fixed up or down sequence.

Question 2

A digital systems engineer needs to represent the decimal value -25 in an 8-bit signed binary format. Using the two's complement method, what is the correct binary representation?

Accepted Answer

11100111

Answer

10011011

Answer

11100110

Answer

00011001

Question 3

In a digital logic circuit, what is the primary functional difference between a combinational circuit and a sequential circuit?

Accepted Answer

A combinational circuit's output depends solely on its current inputs, while a sequential circuit's output depends on both current inputs and its previous state.

Answer

Sequential circuits are constructed exclusively from AND, OR, and NOT gates, whereas combinational circuits incorporate memory elements like flip-flops.

Answer

Combinational circuits require a clock signal for operation, while sequential circuits are asynchronous and do not.

Answer

The speed of a combinational circuit is generally slower than that of a sequential circuit due to the lack of memory.

Question 4

Applying De Morgan's theorem to the Boolean expression (A + B)' ⋅ C simplifies to which of the following expressions?

Accepted Answer

A' ⋅ B' ⋅ C

Answer

(A' ⋅ B') + C'

Answer

A' + B' + C

Answer

(A ⋅ B)' + C

Question 5

A design requires a logic circuit that can store one bit of data and is triggered by a clock signal. However, a known issue with simple JK flip-flops, the 'race-around condition,' must be avoided. Which of the following digital logic components is specifically designed to solve this problem?

Accepted Answer

Master-Slave JK Flip-Flop

Answer

D Latch

Answer

T Flip-Flop

Answer

Full Adder

Question 6

When using a Karnaugh map (K-map) to simplify a Boolean expression, which of the following is a fundamental rule for grouping the 1s (for a Sum-of-Products form)?

Accepted Answer

Each group must contain a number of cells that is a power of 2 (e.g., 1, 2, 4, 8).

Answer

Groups can be formed diagonally to cover more cells.

Answer

Each '1' in the map must belong to only one group to avoid redundancy.

Answer

Groups should be made as small as possible to isolate individual terms.