Semiconductor Diode MCQ Quiz in मल्याळम - Objective Question with Answer for Semiconductor Diode - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

CONCEPT:

• Zener diode: A Semiconductor diode blocks current in the reverse direction, but will suffer from premature breakdown or damage if the reverse voltage applied across becomes too high.

It can operate continuously without being damaged in the region of reverse biased

Functions:

1) It acts as a voltage regulator

2) In forward biasing it acts as an ordinary diode.

The current flowing through the Zener diode is given by the following formula:

\({{\rm{I}}_{\rm{Z}}} = {{\rm{I}}_{{{\rm{R}}_{\rm{i}}}}} - {{\rm{I}}_{{{\rm{R}}_{\rm{L}}}}}\)

CALCULATION:

When the power supply is 120 V,

Here zener voltage = 50 V

The voltage across 5 KΩ is:

VRi = Power supply – Zener voltage

⇒ VRi = 120 – 50

∴ VRi = 70 V

Now, the current through Ri is:

\({{\rm{I}}_{{{\rm{R}}_{\rm{i}}}}} = \frac{{{{\rm{V}}_{{\rm{Ri}}}}}}{{{{\rm{R}}_{\rm{i}}}}}\)

\(\Rightarrow {{\rm{I}}_{{{\rm{R}}_{\rm{i}}}}} = \frac{70}{{5000}} = 14 mA\)

∴ Current through series resistance = IRi = 14 mA

The voltage across RL is:

VRL = Zener voltage

∴ VRL = 50 V

Now, the current through RL = V_RL =  50/10000 = 5 mA

So option 3 is correct

CONCEPT:

Diode:

• A diode is a semiconductor device that essentially acts as a one-way switch for current.
  • It allows current to flow easily in one direction but severely restricts current from flowing in the opposite direction.

Forward biasing:

• In the forward bias, the p side of the diode is connected to the positive side of the battery and the n side is connected to the negative side of the battery.
• The direction of the applied voltage is opposite to the junction barrier potential. Therefore, the size of the depletion region decreases.
• The current in forward biasing is given by,

⇒ I = I_s(e^eV/kT - 1)

Where I_s = Saturation current, In the exponent e = 1.6×10^-19 C, and k = Boltzmann's constant

• Cut-in (Knee) voltage:
  • The voltage at which the current starts to increase rapidly in forward biasing.
  • For Ge it is 0.3 V and for Si it is 0.7 V.

EXPLANATION:

• Cut-in (Knee) voltage:
  • The voltage at which the current starts to increase rapidly in forward biasing.
  • For Ge it is 0.3 V and for Si it is 0.7 V.

• Hence, option 1 is correct.

CONCEPT:

• Zener diodes are normal PN junction diodes operating in a reverse-biased condition.
  • Working of the Zener diode is similar to a PN junction diode in forwarding biased condition, but the uniqueness lies in the fact that it can also conduct when it is connected in reverse bias above its threshold/breakdown voltage.
  • It is operated in a breakdown region.

• Peltier-diode: it uses the Peltier effect for giving or removing heat from the system by applying a voltage across it 
  • It is operated in a forward region
• A light-emitting diode (LED): The device which is used to produce the different intensity of light and different colour depending upon the types of mater used in making it is called LED.
  • It is operated in a forward region
• Laser  diode: It is just like a LED by produce highly energetic, polarized, monochromatic intense beam of light 
  • It is operated in a forward region

Explanation:

From the above explanation, we can see that Zener diode is the only one which can work in a breakdown region and can be used as voltage regulator  as shown below.

Hence option 1 is correct among all

Extra points:

Zener diode is called Voltage regulator diode cause it maintains a constant voltage across its terminals called Zener voltage once the breakdown happens.

• Zener diode: A Semiconductor Diode blocks current in the reverse direction, but will suffer from premature breakdown or damage if the reverse voltage applied across becomes too high.

• Zener diode as voltage regulator: The Zener diode is connected with its cathode terminal connected to the positive rail of the DC supply so it is reverse biased and will be operating in its breakdown condition. Resistor Rs is selected so to limit the maximum current flowing in the circuit.

CONCEPT:

• Zener diodes are normal PN junction diodes operating in a reverse-biased condition.
  • Working of the Zener diode is similar to a PN junction diode in forward biased condition, but the uniqueness lies in the fact that it can also conduct when it is connected in reverse bias above its threshold/breakdown voltage.
  • It is operated in a breakdown region.

• Photo-diode: It is a light-sensing device which is used to sense the intensity of light
  • Some of the examples are the smoke detector, a receiver in tv for converting remote signals, etc.
• Normal P-N junction diode: just like Zener diode when semiconductors of P and N-type doping is combined such devices are called p-n junction diode but unlike Zener diode, this types of diode do not work in reverse bias
• A light-emitting diode (LED): The device which is used to produce the different intensity of light and different colour depending upon the types of mater used in making it is called LED.

Some symbols:

1)     Zener diodes

2)     Normal P-N junction

3)     A light-emitting diode (LED)

4)             Photo-diode

5)      Schottky Diode

EXPLANATION:

From the above given symbols, denotes the zener diode.

CONCEPT:

• Zener diodes are heavily doped than ordinary diodes.
  • Zener diodes have an extra thin depletion region.
  • It is a silicon semiconductor device that permits current to flow in either a forward or reverse direction.

EXPLANATION:

• Zener diodes allow current to flow in either a forward or reverse direction.
• The junction in the Zener diode breaks down when potential reaches the Zener Voltage and the voltage across the terminals of a Zener diode is reversed.
• This is why it is also known as a breakdown diode.
• This makes the current flow in the reverse direction also.
• So the correct answer is option 3.

The correct answer is Diode design

Concept:

In a p-n junction, holes are majority carriers in p-side and electrons are majority carriers in the n-side. This is as shown:

• As there is a high electron and hole concentration in n-type and p-type near the junction, diffusion takes place because of the concentration gradient, i.e. holes diffuse from p-type region to the n-type region and vice-versa.

• Barrier Potential of P -n Junction: The electric potential difference across the P-N Junction is called Barrier Potential.

• Doping: The addition of impurities in a semiconductor to change its conductivity and other properties is known as dopping.
• Barrier Potential depends upon 

1. Materials used to make PN Junction: For silicon, it is 0.7 V for Germanium it is 0.3 V at room temperature.
2. Amount of dopping done: The amount of dopping will decide the amount of majority charge carriers in the junction.
3. Temperature: Increase in temperature will change the number of minority charge carriers. 

• The electric field formed in the depletion region acts as a barrier
• This barrier is formed when some of the free electrons in the n-region diffuse across the junction and combine with holes to form negative ions
• The development of barrier potential in the depletion zone of a PN junction is consequent to diffusion of majority carriers across the junction

Explanation:

Barrier potential is given by\({V_{th}} = \frac{{kT}}{q}\ln \left( {\frac{{{N_A}{N_D}}}{{N_i^2}}} \right)\)

• It is dependent on temperature, doping, and the bias voltage applied across barrier but not on diode shape or design.

CONCEPT:

• Diode: A diode is a two-terminal electronic component that conducts current primarily in one direction; it has low resistance in one direction, and high resistance in the other.

There are two 

• Forward Biasing: 
  • The forward bias means the positive region is connected to the p-terminal of the supply and the negative region is connected to the n-terminal of the supply.
  • In forward biasing the external voltage is applied across the PN-junction diode. 
• Reverse Biasing: 
  • ​In reversed bias, the negative region is connected to the positive terminal of the battery and the positive region is connected to the negative terminal. ​
  •  It creates a high resistive path in which no current flows through the circuit.

CALCULATION:

Given R₁ = 10Ω, R₂ = 20Ω 

• The diode D₁ is forward biased and D₂ is reverse biased, so Diode D₁ will allow the current, and  D₂ doesn't. 
• Current can be calculated as 

\(\Rightarrow I =\frac{V}{R}=\frac{5}{10}= 0.5 A\)

• The current supplied by the battery is 0.5 A.

CONCEPT:

•  The special kind of diode, which permits current to flow not only in the forward direction but also allows current to flow in the reverse direction is called Zener diode.

Power of a Zener diode is given by:

P_max = V_z I_max

Where V_z is potential drop across diode and I_max is the maximum current in the diode.

CALCULATION:

Given that: Potential drop (V_z) = 6.2 V 

P_max = 1 W

In Zener diode, the max rated power is given by \({{\rm{P}}_{\max }} = {V_Z}{I_{max}}\)

\({I_{max}} = \frac{{1W}}{{6.2V}} = 161\;mA\) so option 2 is correct.