Practice Test Geeks(CET) Certified Electronics Technician Practice Test
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Staging & Prognostic Factors Flashcards

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  1. Which factor most significantly determines the input impedance of a common-emitter transistor amplifier stage?

    Answer: Base bias resistors and transistor beta

    The input impedance of a CE stage is primarily set by the parallel combination of bias resistors and the transistor's beta times the emitter resistance.

  2. An amplifier stage has an output impedance of 10 kΩ driving a load of 1 kΩ. What happens to the voltage across the load relative to the open-circuit output voltage?

    Answer: It drops significantly due to loading

    The load forms a voltage divider with the output impedance; with a 10:1 ratio, most voltage drops across the internal impedance.

  3. What is the function of a buffer stage inserted between two amplifier stages?

    Answer: Provide high input impedance and low output impedance to prevent loading

    A buffer stage (often an emitter or source follower) presents high input impedance and low output impedance to isolate stages and prevent loading effects.

  4. In a cascaded amplifier system, thermal noise contributed by each stage:

    Answer: Accumulates and is amplified by subsequent stages

    Noise introduced in early stages is amplified along with the signal by all subsequent stages, making the first stage's noise contribution most critical.

  5. What is the significance of the 'noise figure' (NF) in a multistage receiver front-end?

    Answer: It measures how much the stage degrades signal-to-noise ratio

    Noise figure quantifies the degradation of SNR as a signal passes through the amplifier stage; lower NF means less added noise.

  6. Friis's formula for cascaded noise figures shows that the overall noise figure is dominated primarily by:

    Answer: The first stage

    Friis's formula shows that the first stage's noise figure contributes most to overall system noise, especially when it has low gain.

  7. Which topology is commonly used as the first stage in a low-noise amplifier (LNA) design?

    Answer: Common-emitter with inductive degeneration

    Common-emitter with inductive degeneration provides good noise performance and simultaneous noise and input impedance matching in LNA designs.

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