Most Important Points | Diodes | Part-I | Competitive Examination




Most Important Points | Diodes | Part-I | Competitive Examination


Suitable for the post of Junior Engineer asked in BSNL, DMRC, DRDO, PTCUL, RRB, UPCL, etc examination.

  1. Semiconductors have 4 electrons in their external orbit Example:- Si-14, Ge-32.

  2. Pure semiconductor is called Intrinsic semiconductor.

  3. Doped semiconductor is called Extrinsic semiconductor.

  4. Doping can be done by pentavalent impurity and trivalent impurity.

  5. According to Type of Impurity, semiconductor are of two types: N-type (formed by doping of pentavalent impurities like bismith, arsenic, antimony and phosphorus) and P-type (formed by doping of trivalent impurites like boron, indium, gallium, alluminium).

  6. Si has Forbidden Energy Gap of 1.12 eV and Ge has forbidden energy gap of 0.72 eV.

  7. Semiconductors have negative Temperature Co-efficient of resistance i.e. With increase in temperature their resistance decreases like insulators.

  8. When one half of any semiconductor substrate is dopped with p-type impurity and other half with n-type of impurity, a junction is formed called P-N Junction. This junction acts as barrier for charge carriers to flow from one side to another side.

  9. The process of applying external voltage on both sides of substrate is called Biasing.

  10. When positive dc voltage is applied to p-side and negative voltage is applied to n-side, this biasing is called Forward Biasing.

  11. When negative dc voltage is applied to p-side and positive voltage to n-side, this type of biasing is called Reverse Biasing.

  12. In forward biased, Voltage required to break the barrier is called Knee Voltage which value is 0.72 v for Si and 0.32 v for Ge.

  13. In reverse biased, Voltage required to break the barrier is called Reverse Break-down Voltage.

  14. P-N junction is called a Diode. Diodes are used for switching, rectification, voltage regulation etc.

  15. Depending upon construction and practical application Types of Diodes are zenor diode, light emitting diode, photo diode, tunnel diode, varactor diode etc.




Author and Reference:



Author: Mr. Amarjeet Singh Jamwal, Assistant Loco Pilot, Indian Railway, Ambala Division.

Reference: Albert Malvino, “Electronic Principles”.

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