Digital Circuits Flashcards

Which of the following is a universal gate because it can implement any Boolean function on its own?

Answer: NOR

NOR is a universal gate; using only NOR gates, you can construct NOT, AND, OR, and any other logic function.

In an SR latch built from NOR gates, what happens when both S=1 and R=1 are applied simultaneously?

Answer: Q=0 and Q̄=0 (forbidden state)

With S=R=1 in a NOR-based SR latch, both outputs are forced to 0, which is the forbidden/invalid state because Q and Q̄ are no longer complementary.

A binary ripple counter uses 4 T flip-flops. After 19 clock pulses, what is the counter output (MSB to LSB)?

Answer: 0011

19 in 4-bit binary is 10011₂; a 4-bit counter truncates to the lower 4 bits: 0011 (19 mod 16 = 3 = 0011₂).

What does the term 'fan-out' refer to in digital logic?

Answer: The maximum number of gate inputs that a gate output can reliably drive

Fan-out specifies how many standard gate inputs the output of a given gate can drive while maintaining valid logic levels.

Which circuit converts a BCD (Binary Coded Decimal) input to a seven-segment display output?

Answer: Decoder

A BCD-to-seven-segment decoder takes a 4-bit BCD input and produces the 7 output signals needed to drive the correct segments of a seven-segment display.

In a Moore machine, the output depends on:

Answer: Current state only

In a Moore machine, outputs are functions of the current state only, not the current inputs.

A 4-bit magnitude comparator has inputs A=1010 and B=1010. Which output is asserted?

Answer: A = B

Since A and B are identical (both equal 10 in decimal), the A=B output of the comparator is asserted.