# 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?

• A
• B

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

• A
• B

Q2:

An NPN transistor is connected to a power supply with voltage . A power supply with voltage is connected across the transistor’s emitter and base terminals, as shown in the diagram. There is a current between and the collector terminal, a current between and the emitter terminal, and a current between and the base terminal. Calculate .

• 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 C for the charge of an electron. Answer in scientific notation to one decimal place.

• A s−1
• B s−1
• C s−1
• D s−1
• E s−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?

• A
• B

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

• A
• B

Q4:

An NPN transistor is connected to a power supply with voltage . A power supply with voltage is connected across the transistor’s emitter and base terminals, as shown in the diagram. There is a current between and the collector terminal, a current between and the emitter terminal, and a current between and the base terminal. Calculate .

• 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 to . 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? • A
• B
• CBoth regions are forward biased.

Q6:

An NPN transistor is connected to a power supply with voltage . A power supply with voltage is connected across the transistor’s emitter and base terminals, as shown in the diagram. There is a current between and the collector terminal, a current between and the emitter terminal, and a current between and the base terminal. An external resistance is placed between and the collector terminal, and an external resistance is placed between and the base terminal. The potential difference across the collector and emitter terminals is . If the value of is reduced, which of the following most correctly describes the effect on the value of ?

• A increases.
• B decreases.
• C is constant.

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

• A is constant.
• B increases.
• C 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? • A
• B
• CBoth regions are reverse biased.