Worksheet: Transistors

In this worksheet, we will practice describing how transistors can be used as electrical switches in circuits.

Q1:

An NPN transistor is connected to a direct current source, as shown in the diagram. The two n-regions are identical.

Which of the regions of the transistor is the collector region?

  • AN
  • BN

Which of the regions of the transistor is the emitter region?

  • AN
  • BN

Q2:

An NPN transistor is connected to a power supply with voltage 𝑉CC. A power supply with voltage 𝑉EB is connected across the transistor’s emitter and base terminals, as shown in the diagram. There is a current 𝐼=99.5CmA between 𝑉CC and the collector terminal, a current 𝐼E between 𝑉EB and the emitter terminal, and a current 𝐼=0.5BmA between 𝑉EB and the base terminal.

Calculate 𝐼E.

  • A100.5 mA
  • B99.5 mA
  • C50 mA
  • D50.5 mA
  • E100 mA

Find the rate at which free electrons diffusing through the base region recombine with holes. Use 1.6Γ—10 C for the charge of an electron. Answer in scientific notation to one decimal place.

  • A3.1Γ—10 sβˆ’1
  • B1.1Γ—10 sβˆ’1
  • C3.4Γ—10 sβˆ’1
  • D3.3Γ—10 sβˆ’1
  • E1.3Γ—10 sβˆ’1

Q3:

A PNP transistor is connected to a direct current source, as shown in the diagram. The two p-regions are identical.

Which of the regions of the transistor is the collector region?

  • AP
  • BP

Which of the regions of the transistor is the emitter region?

  • AP
  • BP

Q4:

An NPN transistor is connected to a power supply with voltage 𝑉CC. A power supply with voltage 𝑉EB is connected across the transistor’s emitter and base terminals, as shown in the diagram. There is a current 𝐼=99.5CmA between 𝑉CC and the collector terminal, a current 𝐼=100.0EmA between 𝑉EB and the emitter terminal, and a current 𝐼B between 𝑉EB and the base terminal.

Calculate 𝐼B.

  • A100.5 mA
  • B100 mA
  • C199.5 mA
  • D5 mA
  • E0.5 mA

The dc current gain of the transistor is equal to the ratio of 𝐼C to 𝐼B. Calculate the dc current gain of the transistor.

Q5:

An NPN transistor is connected to a direct-current source, as shown in the diagram. Which of the two identical n-regions of the transistor is forward biased?

  • AN
  • BN
  • CBoth regions are forward biased.

Q6:

An NPN transistor is connected to a power supply with voltage 𝑉CC. A power supply with voltage 𝑉EB is connected across the transistor’s emitter and base terminals, as shown in the diagram. There is a current 𝐼C between 𝑉CC and the collector terminal, a current 𝐼E between 𝑉EB and the emitter terminal, and a current 𝐼B between 𝑉EB and the base terminal. An external resistance 𝑅C is placed between 𝑉CC and the collector terminal, and an external resistance 𝑅B is placed between 𝑉EB and the base terminal. The potential difference across the collector and emitter terminals is 𝑉CE.

If the value of 𝑅B is reduced, which of the following most correctly describes the effect on the value of 𝐼C?

  • A𝐼C increases.
  • B𝐼C decreases.
  • C𝐼C is constant.

If the value of 𝑅B is increased, which of the following most correctly describes the effect on the value of 𝐼C?

  • A𝐼C is constant.
  • B𝐼C increases.
  • C𝐼C decreases.

Q7:

A PNP transistor is connected to a direct-current source, as shown in the diagram. Which of the two identical p-regions of the transistor is reverse biased?

  • AP
  • BP
  • CBoth regions are reverse biased.

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