Analog and Digital Electronics Flashcards

In a binary-weighted DAC with a 4-bit input, the MSB resistor is R. What is the resistor value for the LSB?

Answer: 8R

In a binary-weighted DAC, each bit's resistor doubles relative to the more significant bit, so the LSB resistor = 8R for a 4-bit DAC with MSB resistor R.

A push-pull Class B power amplifier has crossover distortion because:

Answer: Each transistor only conducts for 180° and the 0.6–0.7V base-emitter threshold creates a dead zone near zero

Neither transistor conducts when the input is within ±0.6-0.7V of zero, creating a nonlinear dead band (crossover distortion) in the output.

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

Answer: 2

A 4-to-1 MUX requires 2 select lines because 2² = 4 unique combinations address all 4 inputs.

In a successive approximation ADC (SAR ADC), converting a 0.7V input with a 1V reference and 3-bit resolution, the first trial bit sets:

Answer: 100

SAR always starts by setting the MSB to 1 (100), comparing 0.5V against 0.7V — since 0.7 > 0.5, the MSB is kept.

Which of the following describes a key advantage of CMOS logic over NMOS logic?

Answer: Near-zero static power dissipation

CMOS draws negligible static current because the pull-up (PMOS) and pull-down (NMOS) networks are never simultaneously fully on in steady state.

The Miller effect in an inverting amplifier causes the input capacitance to appear as:

Answer: Cf · (1 + |Av|)

Miller's theorem shows that a feedback capacitor Cf across an inverting amplifier appears at the input as Cf·(1 + |Av|), significantly increasing effective input capacitance.

A Johnson (twisted-ring) counter with 4 flip-flops produces how many unique states?

Answer: 8

A Johnson counter with N flip-flops generates 2N unique states, so 4 flip-flops produce 8 states.