Question

An ideal Zener diode with breakdown voltage of \(3\,\text{V}\) is reverse biased with a negative input voltage \(V_1=-5\,\text{V}\). The magnitude of voltage difference between points \(B\) and \(A\) is:

• A. \(0\,\text{V}\)
• B. \(3\,\text{V}\)
• C. \(2\,\text{V}\)
• D. \(1\,\text{V}\)

Hint:

An ideal Zener diode maintains a constant voltage equal to its breakdown voltage. Always check whether the applied reverse voltage exceeds the breakdown voltage. If breakdown occurs, the voltage across the diode becomes constant. Zener diodes are widely used as voltage regulators.

Answer 1

The Correct Option is B

Concept:

• A Zener diode is specially designed to operate in the reverse breakdown region.

• When the reverse voltage across the diode exceeds the Zener breakdown voltage, the diode starts conducting heavily.

• In the breakdown region, the voltage across the Zener diode remains nearly constant and equal to its breakdown voltage.

• This property makes the Zener diode useful as a voltage regulator.

Step 1: Identify the operating condition of the Zener diode
The given breakdown voltage is \[ V_Z=3\,\text{V} \] The applied reverse voltage is \[ V_1=-5\,\text{V} \] Since \[ |V_1|=5\,\text{V}\gt V_Z=3\,\text{V} \] the diode operates in the reverse breakdown region.

Step 2: Apply the property of an ideal Zener diode
For an ideal Zener diode operating in breakdown, \[ V_{BA}=V_Z \] The voltage across the diode remains fixed at its breakdown voltage irrespective of further increase in reverse voltage.

Step 3: Calculate the voltage difference between B and A
Therefore, \[ |V_{BA}|=3\,\text{V} \]

Step 4: Select the correct option
The magnitude of voltage difference between points \(B\) and \(A\) is \[ \boxed{3\,\text{V}} \] Hence, the correct answer is \[ \boxed{\text{Option (B)}} \]