Question

What is true for an ideal transistor switch when turned $\text{OFF}$?

• A. It has an infinite resistance.
• B. It has low resistance.
• C. It has maximum current flow.
• D. It has zero current flow.

Answer 1

Answer: (A), (D)

It has zero current flow.

A transistor can be used as a switch. When turned off, it behaves as if it is disconnected from the circuit, like an open circuit. No current flows through it.

$\therefore \text{Current}=0$.

$\because \text{Current}\propto \frac{1}{\text{Resistance}}$

$\therefore \text{Current}=0\Rightarrow \text{Resistance}=\infty$

Hence, $\left(A\right)$ and $\left(D\right)$ are the correct answers.