Digital Electronics and Systems Flashcards

Which digital logic family is best suited for extremely high-speed applications due to its non-saturating transistor operation?

Answer: ECL (Emitter-Coupled Logic)

ECL keeps transistors out of saturation, eliminating storage time and enabling propagation delays as low as 1 ns.

In digital system design, what is 'fan-out' defined as?

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

Fan-out specifies how many standard inputs of the same logic family a single gate output can drive without exceeding its current sourcing/sinking limits.

A multiplexer (MUX) with 4 data inputs requires how many select lines?

Answer: 2

A 4-to-1 MUX needs 2 select lines because 2 bits can encode 4 unique states (2² = 4).

What does 'propagation delay' measure in a digital logic gate?

Answer: Time between an input change and the corresponding output change

Propagation delay (tpd) is the time measured from when an input transitions to when the output reaches its new valid logic level.

In a PLD (Programmable Logic Device), what is the typical structure used to implement sum-of-products expressions?

Answer: Programmable AND array followed by fixed OR array

A PAL (Programmable Array Logic) uses a programmable AND plane to create product terms fed into a fixed OR plane to produce sum-of-products outputs.

Which type of memory retains its contents without a clock refresh cycle and without power?

Answer: Flash (EEPROM)

Flash memory (a type of EEPROM) is non-volatile and retains data indefinitely without power, unlike DRAM or SRAM which are volatile.

What is the minimum number of bits required to represent the decimal number 200 in straight binary?

Answer: 8

2^7 = 128 < 200 ≤ 256 = 2^8, so 8 bits are needed; 200 in binary is 11001000.