Physics Electronics PMDC Conceptual Practice
PMDC Verified Question 149 of 494
To establish forward bias in a PN junction diode, the external DC voltage source must be connected such that:
A
The positive terminal connects to the N-region and the negative terminal to the P-region
B
Both the P-region and N-region are connected to the positive terminal
C
Both the P-region and N-region are connected to the negative terminal
D
The positive terminal connects to the P-region and the negative terminal to the N-region
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: The positive terminal connects to the P-region and the negative terminal to the N-region
Concept:

Forward biasing requires applying an external potential that opposes and reduces the built-in junction barrier potential, which occurs when the P-side is made positive relative to the N-side.

Formula:

$$V_{\text{anode}} - V_{\text{cathode}} > V_0 \quad (\text{Forward Bias})$$

Solution:

  • Connecting the positive battery terminal to the P-region (anode) repels holes toward the junction.


  • Connecting the negative battery terminal to the N-region (cathode) repels electrons toward the junction.


  • This reduces the depletion width and allows substantial forward current to flow once \( V_{\text{ext}} > V_0 \).


Why other options are incorrect:

  • Option A: Connecting positive to N and negative to P creates reverse bias.
  • Option B: Connecting both sides to the positive terminal produces zero net bias across the junction.
  • Option C: Connecting both sides to the negative terminal produces zero potential difference across the junction.

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