CBSE 2025, Compartment, Set 1

Question

With the help of a circuit diagram, describe the method to obtain p-n junction diode characteristic when it is forward biased. Draw the shape of the characteristic.

Edvaya · Accepted Answer

The correct answer is Subjective. **SOLUTION** **Circuit Diagram Setup:** To obtain the forward-biased V-I characteristics, the p-side of the diode is connected to the positive terminal of the battery, and the n-side is connected to the negative terminal. A voltmeter is carefully connected in parallel across the diode to precisely measure the voltage drop, and a milliammeter ($mA$) is connected in series to record the resulting current. A rheostat (variable resistor) is heavily utilized to gradually vary the applied voltage across the junction. **Description:** The applied voltage is incrementally increased in small steps, and for each step, the corresponding current values are recorded. A graph is then plotted with Voltage on the x-axis and Current on the y-axis. Initially, the current increases very slowly. However, once the applied voltage successfully exceeds the internal barrier potential (e.g., $0.7	ext{ V}$ for Silicon), the diode current begins to increase exponentially. **Shape of Characteristic:** The resultant V-I curve rises non-linearly, showing an exponential "knee" bend where conduction starts.

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Physics > Modern Physics > Semiconductor Electronics

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