1.
An:
2.
An:
3. For the Following questions, answer in one or two sentences. (a) Why should the emitter be doped more heavily than the base? An: To improve the emitter injection efficiency; and to reduce the back injected carriers from B‐E. (b) “The base width is small” is often stated in device analysis. What is it being compared with? An: “Small” means WB << LB, typically < 1 µm. (c) If the base width, WB, were made smaller, explain how it would affect the base width modulation. An: The depletion with in base, ΔWB, would become a larger portion of WB. Therefore, it would increase the slope of output characteristics. (d) For a NPN device, indicate the voltage polarity (+, ‐) for the following:
Region VEB VCB
Active ‐ (forward bias) + (reverse bias)
Saturation ‐ (forward bias) ‐ (forward bias)
Cutoff + (reverse bias) + (reverse bias)
Remember:
(e) For a PNP device, indicate the voltage polarity (+, ‐) for the following: An:
Region VEB VCB
Active + ‐
Saturation + +
Cutoff ‐ ‐
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