CABT Fundamentals of Electronics 3 — Questions and Answers
Question 1: In a full-wave bridge rectifier, how many diodes are required?
- 1
- 2
- 4 (Correct answer)
- 6
Correct answer: 4
A full-wave bridge rectifier uses 4 diodes arranged so that current flows through the load in the same direction for both AC half-cycles.
Question 2: What is the primary advantage of using a switching power supply over a linear power supply in biomedical equipment?
- Lower output ripple
- Higher efficiency and smaller size (Correct answer)
- Better regulation at all loads
- Lower electromagnetic interference
Correct answer: Higher efficiency and smaller size
Switching power supplies operate at high frequencies allowing smaller transformers and capacitors, resulting in higher efficiency (often >85%) and reduced size/weight.
Question 3: A Wheatstone bridge is balanced when:
- R1/R2 = R3/R4 (Correct answer)
- R1 + R2 = R3 + R4
- R1 × R2 = R3 × R4
- R1 - R2 = R3 - R4
Correct answer: R1/R2 = R3/R4
The Wheatstone bridge is balanced (zero galvanometer current) when the ratio of resistances in each arm are equal: R1/R2 = R3/R4.
Question 4: In digital logic, what is the output of a NAND gate when both inputs are HIGH?
- HIGH
- LOW (Correct answer)
- Undefined
- Depends on supply voltage
Correct answer: LOW
A NAND gate outputs LOW only when all inputs are HIGH; it is the complement of an AND gate.
Question 5: What phenomenon occurs when an AC signal causes a transistor to conduct during only part of the input cycle in Class B amplification?
- Crossover distortion (Correct answer)
- Harmonic distortion
- Intermodulation distortion
- Phase distortion
Correct answer: Crossover distortion
Crossover distortion occurs at the zero-crossing point in Class B push-pull amplifiers due to the transistor's 0.6V threshold voltage.
Question 6: A 12-bit ADC with a 5V reference voltage has a resolution of approximately:
- 0.122 mV
- 1.22 mV (Correct answer)
- 12.2 mV
- 122 mV
Correct answer: 1.22 mV
Resolution = Vref / 2^n = 5V / 4096 ≈ 1.22 mV per step for a 12-bit ADC.
Question 7: In a biomedical instrumentation amplifier, the primary purpose of the input stage with matched resistors is to:
- Provide high voltage gain
- Achieve very high CMRR and input impedance (Correct answer)
- Reduce output offset voltage
- Filter high-frequency artifacts
Correct answer: Achieve very high CMRR and input impedance
The matched-resistor input stage of an instrumentation amplifier maximizes CMRR and provides high input impedance to avoid loading the signal source.
CABT Fundamentals of Electronics 3
In a full-wave bridge rectifier, how many diodes are required?