Question

The working transistor with its three legs marked $P,Q$, and $R$ is tested using a multimeter. No conduction is found between $P$ and $Q$. By connecting the common (negative ) terminal of the multimeter to $R$ and the other (positive) terminal to $P$ or $Q$, some resistance is seen on the multimeter. The correct statement for the transistor is

• A. It is an $\text{n-p-n}$ transistor with $R$ as base.
• B. It is a $\text{p-n-p}$ transistor with $R$ as collector.
• C. It is a $\text{p-n-p}$ transistor with $R$ as emitter.
• D. It is an $\text{n-p-n}$ transistor with $R$ as collector.

Answer 1

The correct option is A It is an $\text{n-p-n}$ transistor with $R$ as base.

It is given that there is no conduction between $P$ and $Q$, thus there must be some conduction between $PR$ or $QR$.
This claims that $R$ is surely a base.

Moreover, resistance is observed when negative terminal is connected to $R$ and positive terminal to $P$ or $Q$ means that the connection should be reversed biased because the resistance in reversed biasing is very high compared to forward biasing.

Hence, it is an $\text{n-p-n}$ transistor with $R$ as a base.

Hence, $\left(A\right)$ is the correct answer.