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Practice Questions for Basic Electronic Technology (III) - 04730 (National Self-Study Exam, 610201)

To help you prepare for the exam, I’ve compiled a set of practice questions based on past papers. This is a partial extraction from the April 2021 national exam, translated to English for clarity. The exam typically includes 15 single-choice questions (1 point each), 15 fill-in-the-blank questions (1 point each), short-answer questions, calculation problems, and design/analysis questions. Topics cover circuit analysis, semiconductors, amplifiers, operational amplifiers, power supplies, and digital logic.

Focus on understanding concepts like resonance, transistor biasing, op-amp circuits, rectification, and logic gates. Practice calculations and circuit analysis.

Section 1: Single-Choice Questions (15 questions total in full exam; partial here)

Each question is worth 1 point. Choose the correct option.

  1. Among the following voltage waveforms, the one representing a pulsating DC voltage signal is:
    (Note: Refers to typical waveforms; typically, the one with ripple on DC baseline.)

  2. The main reason for zero-point drift in a directly coupled multi-stage amplifier circuit is:
    • A. Resistor value errors
    • B. Dispersion of transistor parameters
    • C. Temperature effects on transistor parameters
    • D. Unstable power supply voltage
  3. For a transistor operating in the active region, if the base current \( I_b \) increases from 12 μA to 22 μA, and the collector current \( I_c \) changes from 1 mA to 2 mA, then its current gain \( \beta \) is approximately:
    • A. 83
    • B. 91
    • C. 100
    • D. 183
  4. To superimpose a DC voltage on a sine wave voltage, the appropriate operational circuit to use is:
    • A. Proportional operation circuit
    • B. Addition/subtraction operation circuit
    • C. Integral operation circuit
    • D. Differential operation circuit
  5. In a non-inverting proportional operation circuit built with an integrated operational amplifier, the input voltage is 1 V. If the feedback resistor is shorted due to some reason, the output voltage of the operational circuit at this time is:
    • A. 0 V
    • B. 1 V
    • C. Positive saturation output
    • D. Negative saturation output
  6. The average voltage measured across the load resistor in a single-phase half-wave rectifier circuit is 4.5 V. Then, the effective value of the transformer’s secondary voltage \( U \) is:
    • A. 5 V
    • B. 7.07 V
    • C. 10 V
    • D. 14.14 V
  7. The linear integrated voltage regulator CW78L15 can provide an output voltage \( U \) and output current \( I \) of:
    • A. \( U = +15 \) V, \( I = 0.1 \) A
    • B. \( U = -15 \) V, \( I = 0.1 \) A
    • C. \( U = +15 \) V, \( I = 0.5 \) A
    • D. \( U = -15 \) V, \( I = 0.5 \) A
  8. The BCD (8421) code corresponding to the decimal number (65)10 is:
    • A. 11100101
    • B. 01100101
    • C. 10000010
    • D. 10000001
  9. In all conditions that determine an event, as long as one or more conditions are met, the event occurs. This belongs to:
    • A. OR logic
    • B. AND logic
    • C. NOT logic
    • D. NOR logic
  10. Among the following statements about minterms, the correct one is:
    • A. For any minterm, only one set of input variable values makes it 1
    • B. For the same variable values, the product of any two minterms is always 1
    • C. Under arbitrary variable values, the sum of all minterms is 0
    • D. For an n-variable logic function, there are n minterms
  11. When the input to a common-anode seven-segment display decoder is 0100, the outputs that are 0 are:
    • A. a, c, f, g
    • B. a, d, e
    • C. b, c, f, g
    • D. g, d, e
  12. The following that belongs to a combinational circuit component is:
    • A. Synchronous counter
    • B. Data comparator
    • C. Shift register
    • D. Asynchronous counter
  13. When designing logic with a PLA, the logic function expression should be expressed as:
    • A. Simplest “AND-OR” expression
    • B. Simplest “OR-AND” expression
    • C. Standard “AND-OR” expression
    • D. Standard “OR-AND” expression

Section 2: Fill-in-the-Blank Questions (15 questions total in full exam; partial here)

Each blank is worth 1 point. Fill in the missing word(s) or value(s).

  1. An inductor with an inductive reactance of 10 Ω, when the frequency of the voltage signal across it increases by 1 time (doubles), its inductive reactance value is __ Ω.

  2. The condition for resonance in an RLC series circuit is __.

  3. A flashlight operates at 3.2 V. When the filament heats up, its resistance is 3.9 Ω. The current provided by the battery is approximately __ A (retain one decimal place).

  4. Among the three basic amplifier circuits constructed with bipolar junction transistors, the one with a voltage amplification factor approximately equal to 1 is the __ amplifier circuit.

  5. When a PN junction is forward-biased, the current is large; when reverse-biased, the current is very small. This characteristic is called the PN junction’s __ characteristic.

  6. Two signals of equal magnitude but opposite polarity are called __ signals.

  7. The input stage of an integrated operational amplifier usually adopts a __ circuit.

(Note: The full exam continues with more fill-ins, short answers like explaining op-amp virtual short/ground, circuit diagrams for analysis, calculations for amplifier gains, rectifier efficiency, and digital design problems like truth tables or Karnaugh maps.)

Tips for Preparation

References

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