Question:

Which of the diode circuit shows correct biasing used for the measurement of dynamic resistance of p-n junction diode :

Updated On: Nov 4, 2025
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The Correct Option is B

Approach Solution - 1

To determine the correct diode circuit used for measuring the dynamic resistance of a p-n junction diode, we need to understand the concept of biasing in diodes.

Concept Explanation:

  • The measurement of dynamic resistance is typically done under forward bias conditions, where a small AC signal is superimposed on the DC biasing voltage across the diode. Under this condition, the diode is forward biased and the dynamic resistance is defined as the reciprocal of the slope of the diode's I-V characteristic curve at a particular operating point.
  • The dynamic resistance r_d is given by the formula: r_d = \frac{\Delta V}{\Delta I} where \Delta V is the small change in voltage and \Delta I is the small change in current.
  • The correct circuit for measuring dynamic resistance should have a DC forward bias, with a means to measure small changes in current and voltage.

Analysis of Options:

  1. Option 1: Incorrect biasing for measuring dynamic resistance.
  2. Option 2:
    This circuit shows a correctly forward-biased diode for measuring dynamic resistance. A small AC input can be applied across the diode in this configuration to measure the changes in current and voltage, hence calculating the dynamic resistance.
  3. Option 3: Incorrect biasing for measuring dynamic resistance.
  4. Option 4: Incorrect biasing for measuring dynamic resistance.

Conclusion:

The correct answer is Option 2, which shows the correct forward biasing configuration necessary for measuring the dynamic resistance of a p-n junction diode. In this circuit, the diode is forward biased, allowing for the measurement of voltage change and current change as required for dynamic resistance calculation.

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Approach Solution -2

To determine which diode circuit shows the correct biasing used for the measurement of dynamic resistance of a p-n junction diode, it's important to understand the following concepts:

  • Forward Bias: In forward bias, the p-side (anode) of a diode is connected to a higher potential relative to the n-side (cathode). This reduces the barrier potential, allowing current to flow through the diode. Forward bias is used to measure the dynamic or differential resistance of a diode.
  • Dynamic Resistance: Also known as small-signal resistance, it is the resistance offered by the diode to an AC signal when it is forward-biased. The dynamic resistance is generally measured by superimposing a small AC signal over a DC voltage in the forward-bias region.

According to the information provided, the correct biasing involves forward-biasing the diode.

Correct Option:

This circuit configuration correctly forward-biases the diode by connecting the p-side to a positive terminal and the n-side to a negative terminal, which is necessary for dynamic resistance measurements.

The other options likely show either reverse bias configurations or non-standard measurement setups which are unsuitable for dynamic resistance measurement.

In conclusion, the correct approach for examining dynamic resistance in diodes is to ensure they are forward-biased, thereby permitting the assessment of small-signal behavior accurately.

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