Virtual Labs

1. What two distinct physical mechanisms are combined to model the total base-emitter capacitance in SPICE?

a: Depletion capacitance and Diffusion capacitance Explanation

Explanation

b: Parasitic capacitance and Package capacitance Explanation

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c: Ohmic capacitance and Series capacitance Explanation

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d: Miller capacitance and Avalanche capacitance Explanation

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2. The Forward Transit Time (`TF`) parameter is most closely related to which physical process?

a: The time it takes for heat to dissipate from the junction. Explanation

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b: The time it takes for minority carriers to cross the base. Explanation

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c: The time it takes for the depletion region to form. Explanation

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d: The time it takes for the junction to break down under reverse bias. Explanation

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3. A high-frequency BJT (a very fast transistor) would be expected to have what kind of Forward Transit Time (`TF`)?

a: A very large transit time Explanation

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b: A very small transit time Explanation

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c: A negative transit time Explanation

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d: A transit time of zero Explanation

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4. When is the base-emitter *diffusion* capacitance at its largest value?

a: When the transistor is in cutoff (off) Explanation

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b: When the B-E junction is reverse-biased Explanation

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c: When the transistor is heavily forward-biased (on) Explanation

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d: It is a constant value and does not change Explanation

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5. When is the base-emitter *depletion* capacitance at its largest value?

a: When the B-E junction is heavily reverse-biased Explanation

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b: When the B-E junction is heavily forward-biased Explanation

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c: When the collector voltage is at its maximum Explanation

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d: It is a constant value and does not change Explanation

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6. For a B-E junction with a linearly graded doping profile, what value would be expected for the grading coefficient (`MJE`)?

a: Approximately one-half Explanation

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b: Approximately one-third Explanation

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c: Exactly one Explanation

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d: Exactly zero Explanation

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7. For an abrupt (step) junction, which plot linearizes the C-V data to allow for parameter extraction?

a: A plot of capacitance versus voltage Explanation

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b: A plot of the inverse of capacitance cubed versus voltage Explanation

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c: A plot of the inverse of capacitance squared versus voltage Explanation

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d: A plot of the log of capacitance versus voltage Explanation

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8. From the slope of the *correct* linearized plot (e.g., inverse capacitance squared vs. voltage), what physical property can be extracted?

a: The junction's doping concentration Explanation

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b: The forward transit time Explanation

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c: The forward beta Explanation

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d: The base resistance Explanation

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9. How does the B-E depletion capacitance change as the *reverse bias* on the B-E junction is increased?

a: It increases, as the depletion region shrinks. Explanation

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b: It decreases, as the depletion region widens. Explanation

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c: It stays the same, as it is a fixed property. Explanation

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d: It becomes the diffusion capacitance. Explanation

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10. Which extracted parameter is the most critical for modeling the high-frequency *gain* (fT) of the transistor?

a: `CJE` (B-E Zero-Bias Capacitance) Explanation

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b: `VJE` (B-E Built-in Potential) Explanation

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c: `TF` (Forward Transit Time) Explanation

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d: `MJE` (B-E Grading Coefficient) Explanation

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Extraction of bipolar SPICE Gummel-Poon parameters related to B-E junction Capacitance-Voltage (C-V)