The value of depletion capacitance on decreasing the reverse bias on varactor diode (A) decreases (B) increases (C) becomes zero (D) does not change

Short Answer

Expert verified
When the reverse bias on the varactor diode decreases, the depletion capacitance increases. Therefore, the correct answer is (B) increases.

Step by step solution

01

Understand the behavior of a varactor diode

A varactor diode consists of a p-n junction, which has a capacitance (called depletion capacitance) when reverse biased. Varactor diodes are commonly used in tuning circuits, such as radio receivers, where the capacitance needs to be adjusted electrically. The depletion capacitance is determined by the width of the depletion region, which in turn depends on the reverse-bias voltage applied across the diode.
02

Relate depletion capacitance to reverse bias voltage

For a varactor diode, the depletion capacitance (C) is inversely proportional to the square root of the reverse bias voltage (Vr) applied across the diode. This relationship can be mathematically represented as: \(C = \dfrac{C_{0}}{\sqrt{1 + \frac{V_{r}}{V_{0}}}}\) Here, \(C_0\) is the capacitance at zero bias, and \(V_0\) is a junction characteristic constant.
03

Analyze the effect of decreasing the reverse bias voltage

Now, let's analyze the effect of reducing the reverse bias voltage on the depletion capacitance. According to the above equation, when we reduce the reverse bias voltage (Vr), the denominator in the equation becomes smaller while the numerator remains constant. As a result, the overall capacitance (C) becomes larger.
04

Choose the correct answer

Based on our analysis, we can conclude that when the reverse bias on the varactor diode decreases, the depletion capacitance increases. So, the correct answer is: (B) increases

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