Question

Which of the following is unipolar transistor?

• A. p-n-p transistor
• B. n-p-n transistor
• C. field effect transistor
• D. point contact transistor

Hint:

FET: voltage-controlled device; BJT: current-controlled device.

Answer 1

The Correct Option is C

The question asks us to identify which among the given options is a unipolar transistor. Let's break down the options:

1. p-n-p transistor: This is a type of bipolar junction transistor (BJT) where the letters represent the types of semiconductor materials used. It uses both electron and hole charge carriers, thus making it a bipolar device.
2. n-p-n transistor: This is another type of bipolar junction transistor (BJT). Like the p-n-p transistor, it utilizes both types of charge carriers (electrons and holes). Hence, it's also a bipolar device.
3. Field Effect Transistor (FET): This transistor controls current using an electric field and works either with electrons or holes, not both. Thus, it is called a unipolar device because it operates with a single type of charge carrier.
4. Point contact transistor: This is an older type of bipolar transistor, where current is carried by both electrons and holes. Thus, it is bipolar, not unipolar.

From the above analysis, it's clear that the Field Effect Transistor (FET) is unipolar because it functions with only one type of charge carrier, unlike BJTs which are bipolar.

Therefore, the correct answer is: Field Effect Transistor (FET)