Question

A 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. Which of the following is true for the transistor?

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

Answer 1

Answer: (A)

Since no conduction is found when multimeter is connected across $P$ and $Q$ it means either both P and Q are $n$ -type or $p$ -type. So, it means $R$ is base.
When R is connected to negative terminal of multimeter and positive terminal to $P$ and $Q$ , then emitter-base junction will conduct to some extent due to reverse biasing, so it means transistor is in p-n with $R$ as base.