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Amplifier and Oscillator Circuits Flashcards

7 cards from real GROL practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Amplifier and Oscillator Circuits flashcards as text

  1. What is the theoretical maximum efficiency of a Class A power amplifier?

    Answer: 50%

    A Class A amplifier biased at the center of its load line has a theoretical maximum efficiency of 50%, though practical circuits typically achieve far less.

  2. Crossover distortion in a Class B push-pull amplifier is caused by:

    Answer: A dead zone near zero crossing where neither transistor conducts

    Crossover distortion occurs because each transistor has a turn-on threshold voltage, creating a brief gap in conduction near the zero crossing of the waveform.

  3. Why are Class C amplifiers used for RF power amplification but not audio amplification?

    Answer: Their high efficiency works with a resonant tank circuit that reconstructs the full sine wave

    Class C amplifiers are very efficient because they conduct for less than 180° of the cycle; the resonant tank circuit stores energy and restores the complete sine wave output.

  4. The conduction angle of a properly biased Class A amplifier is:

    Answer: 360°

    Class A amplifiers are biased so the transistor conducts for the full 360° of the input cycle — the transistor never cuts off.

  5. Class AB amplifiers are preferred over Class B in high-fidelity audio applications because they:

    Answer: Reduce crossover distortion while maintaining better efficiency than Class A

    Class AB biases the transistors slightly into conduction, eliminating the crossover distortion of Class B while still being more efficient than Class A.

  6. Which amplifier class is most appropriate for amplifying a single-sideband (SSB) suppressed-carrier signal?

    Answer: Class A or Class AB, for linear operation

    SSB signals carry information in amplitude variations and require linear amplification to preserve the modulation envelope; Class A and Class AB provide this linearity.

  7. The conduction angle of a Class C amplifier is:

    Answer: Less than 180°

    Class C amplifiers are biased beyond cutoff so they conduct only during a small portion of the input cycle, giving a conduction angle less than 180°.