Which transistor type is described as involving current in the base controlling main current from Collector to Emitter?

Which transistor type is described as involving current in the base controlling main current from Collector to Emitter?

• A. PNP
• B. NPN
• C. JFET
• D. MOSFET

Answer: (B)

Transistors that are controlled by a small current at the base are Bipolar Junction Transistors, where that base current modulates a much larger current flowing from collector to emitter. The statement describes a device where the base current acts as the control input for the main current path, which is the hallmark of a BJT. Between the two BJT polarities, the NPN version is the one that conducts when a small current is driven into the base with the emitter-base junction forward biased; this base current gates a much larger collector-emitter current. The relation Ic ≈ β Ib shows how a tiny base current controls a much larger main current. In contrast, the PNP version would have the base current flowing out of the base, not into it, so the phrasing “current in the base” aligns with NPN. The other two options are field-effect transistors, where the main current is controlled by a voltage at the gate, not by a base current. That’s why they don’t fit this description.

Transistors that are controlled by a small current at the base are Bipolar Junction Transistors, where that base current modulates a much larger current flowing from collector to emitter. The statement describes a device where the base current acts as the control input for the main current path, which is the hallmark of a BJT.

Between the two BJT polarities, the NPN version is the one that conducts when a small current is driven into the base with the emitter-base junction forward biased; this base current gates a much larger collector-emitter current. The relation Ic ≈ β Ib shows how a tiny base current controls a much larger main current. In contrast, the PNP version would have the base current flowing out of the base, not into it, so the phrasing “current in the base” aligns with NPN.

The other two options are field-effect transistors, where the main current is controlled by a voltage at the gate, not by a base current. That’s why they don’t fit this description.