Answer: Very thin with low doping (lightly doped).
- A Very thick with high doping in standard practice
- B Very thin with low doping (lightly doped)
- C Same as emitter under most conditions encountered
- D Not connected as frequently observed in practice
Correct answer: B. Very thin with low doping (lightly doped)
Explanation: BJT base: very thin (~1 micrometer), lightly doped. Most carriers injected from emitter pass through base to collector without recombining.
Conductors have overlapping bands, semiconductors have a small energy gap that can be bridged by heat or doping, and insulators have a large gap that blocks conduction.
Concept context
Band theory, p-n junction, diodes, transistors, logic gates, and integrated circuits.