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P-N junction diode

A P-N junction diode is a basic diode. It is the combination of P-type and N-type semiconductor.

symbol :


03250

P-N junction and potential barrier :


A P-N junction is the basic building block of many semiconductor devices like diodes and transistors. P-n junctions are formed by joining n-type and p-type semiconductor materials.

Since the n-type region has a high electron concentration and the p-type a high hole concentration this difference in concentration creates density mismatch across junction which results to creation of potential barrier. The value of potential barrier vb is 0.3 for germanium and 0.7 for silicon.

155124-85852-forward-biasing-pn-junction-diodeWorking :

Forward bias:

Application of positive charge at p-side pushes holes towards potential barrier and similarly negative charge at N-side pushes electrons towards barrier if input voltage is grater than potential barrier then electrons diffuse from the n-type side to the p-type side. Similarly, holes flow by diffusion from the p-type side to the n-type side and conduction takes place.

Reverse bias:

If diode is connected in reverse bias holes are attracted towards negative side and electrons are attracted towards positive side then there is no majority carriers in either P-side or N-side which results in creation of depletion region with no majority carriers left then there is no conduction. But, there will be very negligible amount of current passed across diode  due to minority charge carriers.

char diode.jpg

Applications:

      P-N junction diode as Rectifier

  • It is used in clipping and wave shaping circuits in computers, radios, radars etc.…
    • It is used as switches in digital logic designs.
    • It is used in detector and demodulator circuits.
    • It is used in clamping circuits in TV receivers as well as voltage multipliers.
    • It is used as rectifiers in DC power supply manufacturing.

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Comments

  1. ZishanSeptember 14, 2016 at 12:09 PM

    What is a virtual ground?

    ReplyDelete
  2. vikasgurlinkaSeptember 17, 2016 at 2:17 PM

    The real Ground has 2 properties:
    1. It is an infinite current sink
    2. Its voltage is zero

    the term virtually ground mean, its not physically connected to Ground but voltage at that point/node is ‘0V’ so we can consider it as virtual Ground.
    This concept is used for Analysis of Operational Amplifier Circuits(inverting op-amp).
    i'll suggest you to refer Operational Amplifier as differentiator.

    ReplyDelete
  3. Diode | THE JARGONSeptember 17, 2016 at 3:04 PM

    […] P-N junction diode […]

    ReplyDelete
  4. BJT (bipolar junction transistor) | THE JARGONSeptember 24, 2016 at 3:54 PM

    […] The electron in emitter region(n-type) are repelled from the negative terminal of the battery towards junction and enters in to base region(p-type) as junction is in forward biased condition acts same as P-N junction diode. […]

    ReplyDelete

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