BEE BEE Bachelor of Electrical Engineering Analog and Digital Electronics Questions and Answers 2 — Questions and Answers
Question 1: What is the primary advantage of using CMOS logic over TTL logic in digital circuits?
- Lower static power consumption (Correct answer)
- Higher switching speed
- Simpler fabrication process
- Better noise immunity at high frequencies
Correct answer: Lower static power consumption
CMOS logic consumes negligible static power because one of the complementary transistors is always off, drawing almost zero current in steady state.
Question 2: In a common-emitter amplifier, what is the effect of adding an unbypassed emitter resistor?
- Increases voltage gain and decreases input impedance
- Decreases voltage gain and increases input impedance (Correct answer)
- Increases both voltage gain and input impedance
- Decreases both voltage gain and input impedance
Correct answer: Decreases voltage gain and increases input impedance
An unbypassed emitter resistor introduces negative feedback, which reduces voltage gain but increases input impedance and improves stability.
Question 3: Which flip-flop is commonly used to eliminate metastability issues in clock domain crossing designs?
- JK flip-flop
- T flip-flop
- Two-stage synchronizer using D flip-flops (Correct answer)
- SR latch
Correct answer: Two-stage synchronizer using D flip-flops
A two-stage synchronizer with back-to-back D flip-flops allows the potentially metastable output of the first stage to settle before being sampled by the second.
Question 4: What does the Barkhausen criterion state for sustained oscillation in a feedback circuit?
- Loop gain must be greater than unity and phase shift must be 360 degrees
- Loop gain must equal unity and total phase shift must be a multiple of 360 degrees (Correct answer)
- Loop gain must be less than unity and phase shift must be 180 degrees
- Loop gain must equal zero and phase shift must be 90 degrees
Correct answer: Loop gain must equal unity and total phase shift must be a multiple of 360 degrees
The Barkhausen criterion requires the loop gain magnitude to be exactly one and the total phase shift around the loop to be 0° or a multiple of 360° for sustained oscillations.
Question 5: In a 4-bit binary weighted DAC with a reference voltage of 10V, what is the resolution (smallest voltage step)?
- 0.625 V (Correct answer)
- 1.25 V
- 0.5 V
- 2.5 V
Correct answer: 0.625 V
Resolution equals Vref divided by 2^n, so 10V / 16 = 0.625V for a 4-bit DAC.
Question 6: What is the purpose of a Schmitt trigger in digital circuits?
- To amplify weak digital signals
- To convert analog signals to digital with hysteresis for noise immunity (Correct answer)
- To store a single bit of data
- To multiplex multiple input signals
Correct answer: To convert analog signals to digital with hysteresis for noise immunity
A Schmitt trigger uses hysteresis with two different threshold voltages to provide clean digital output from noisy or slowly changing input signals.
BEE BEE Bachelor of Electrical Engineering Analog and Digital Electronics Questions and Answers 2
What is the primary advantage of using CMOS logic over TTL logic in digital circuits?