Virtual Labs

1. In a BJT, which terminals control the flow of current between the other two terminals?

a: Emitter controls collector and base Explanation

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b: Base controls current between collector and emitter Explanation

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c: Collector controls emitter current Explanation

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d: All three equally control current Explanation

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2. Which statement about an NPN BJT is correct?

a: The collector is always negatively doped. Explanation

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b: The base is thin and lightly doped compared to emitter and collector. Explanation

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c: The emitter is lightly doped to allow easy carrier diffusion. Explanation

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d: Base-collector junction is always forward-biased. Explanation

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3. What is the approximate typical range of DC current gain (β) for BJTs used in small-signal amplifiers?

a: 1 - 5 Explanation

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b: 5 - 20 Explanation

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c: 20 - 300 Explanation

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d: 300 - 2000 Explanation

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4. Which of the following describes the forward-active region in a BJT?

a: Both junctions reverse-biased Explanation

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b: Emitter-base forward-biased, collector-base reverse-biased Explanation

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c: Both junctions forward-biased Explanation

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d: Emitter-base reverse-biased, collector-base forward-biased Explanation

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5. If β = 100 and base current I_B = 20 μA in the forward-active region, what is the collector current I_C?

a: 0.2 mA Explanation

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b: 2.0 mA Explanation

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c: 200 mA Explanation

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d: 20 mA Explanation

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6. In saturation mode of a BJT, which condition is true?

a: V_BE is negative Explanation

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b: V_BC is reverse-biased Explanation

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c: Both V_BE and V_BC are forward-biased Explanation

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d: Base current is zero Explanation

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7. What is the Early effect in BJTs?

a: Increase in β at low temperatures Explanation

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b: Reduction of base width with increasing V_CE Explanation

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c: Decrease in collector current with higher V_CE Explanation

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d: Complete cutoff of current at high V_CE Explanation

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8. In a BJT, minority carrier injection from the emitter to base depends primarily on:

a: Emitter doping and V_BE Explanation

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b: Collector doping Explanation

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c: Base resistance only Explanation

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d: Temperature alone Explanation

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9. For a BJT amplifier designed for maximum gain, which parameter combination is preferred?

a: Thick base, low emitter doping Explanation

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b: Thin base, high emitter doping, high β Explanation

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c: Thick emitter, low β Explanation

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d: Wide collector-base depletion region Explanation

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Bipolar Junction Transistors