# Electronic Devices and Circuits Questions and Answers – Tunnel Diodes and its Characteristics

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Tunnel Diodes and its Characteristics”.

1. If ‘X’ corresponds to a tunnel diode and ‘Y’ to an avalanche diode, then__________
a) X operates in reverse bias and Y operates in forward bias
b) X operates in reverse bias and Y operates in reverse bias
c) X operates in forward bias and Y operates in forward bias
d) X operates in forward bias and Y operates in reverse bias

Explanation: In forward bias, negative resistance helps for tunnel diode to operate. Here, the current decreases with increase in voltage. If they are used in reverse bias, they are called as back diodes. Avalanche diode operates in reverse bias at breakdown region.

2. The range of tunnel diode voltage VD, for which slope of its V-I characteristics is negative would be? (The VP is the peak voltage and VV is the valley voltage).
a) VD > 0
b) 0D < VP
c) VV > VD > VP
d) VD > VV

Explanation: In tunnel diode characteristics, the slope is negative in the region between VV and VP. Here, it offers negative resistance. The characteristics are depicted below:

3. Tunnel diode has a very fast operation in__________
a) gamma frequency region
b) ultraviolet frequency region
c) microwave frequency region

Explanation: Tunnel diode is a type of semiconductor which works on tunneling effect of electrons in microwave region. So, tunnel diode has a very fast operation in microwave region.

4. Which of the following are true about a tunnel diode?
1) it uses negative conductance property
2) it operates at high frequency
3) fermilevel of p side becomes higher than the n side in forward bias
a) 1 only
b) 1 and 2
c) 3 only
d) 2 and 3

Explanation: The negative resistance property helps in the operation of tunnel diode. As the tunnel diode works at high frequency, its applications are mostly in that range. High frequency oscillators are based on the resonant tunneling diode.

5. The depletion layer of tunnel diode is very small beacause______
a) its abrupt and has high dopants
b) uses positive conductance property
c) its used for high frequency ranges
d) tunneling effect

Explanation: When the P and N regions are very highly doped, the depletion layer comes closer. The tunnel diode is also highly doped. Its doping concentration varies within a small scale. So it’s an abrupt diode. For these reasons, the depletion region is small.

6. With interments of reverse bias, the tunnel current also increases because________
a) electrons move from balance band of pside to conduction band of nside
b) fermi level of pside becomes higher than that of nside
c) junction currrent decreases
d) unequality of n and p bandedge

Explanation: When the forward bias is increased, the tunnel current is also increased upto a certain limit. This happens when the electron movement takes place from P to N side.

7. The tunnneling involves_______
a) acceleration of electrons in p side
b) movement of electrons from n side conduction band to p side valance band
c) charge distribution managementin both the bands
d) positive slope characteristics of diode

Explanation: Tunneling means a direct flow of electrons across small depletion region from N side conduction band to P side valance band. The electrons begin to accelerate in the N side of the semiconductor.

8. Tunnel diodes are made up of________
a) Germanium and silicon materials
b) AlGaAs
c) AlGaInP
d) ZnTe

Explanation: Germanium and silicon materials have low band gaps and flexibility. That matches tunnel diode requirements. The remaining materials emits the energy in terms of light or heat.

9. For a tunnel diode, when ‘p’ is probability that carrier crosses the barrier, ’e’ is energy,’w’ is width.
a) p ∝ e(-A*e*w)
b) p ∝ 1/ e(-A*e*w)
c) p ∝ e(A*e*w)
d) p ∝ 1/e(A*e*w)

Explanation: The carrier jump occurs without any loss of energy due to small depletion layer. The probability of the carrier to jump across a barrier depends on the energy and width of the band. This variess exponentially for a given carrier.

10. In the construction of tunnnel diode,why is the pellet soldered to anode contact and a tindot to cathode contact via a mesh screen?
a) for better conduction and reduce inductance respectively
b) for heat dissipation and increase conduction respectively
c) for heat dissipation and reduce induction respectively
d) for better conduction and reduce inductance respectively

Explanation: Anode goes through better heat dissipation. So the pellet is used for the purpose. The tindot via mesh screen resists inductive effects caused at the cathode. Conduction is an independent factor which can’t be controlled.

11. What happens to a tunnel diode when the reverse bias effect goes beyond the valley point?
a) it behaves as a normal diode
b) it attains increased negative slope effects
c) reverse saturation current increases
d) beacomes independent of temperature

Explanation: After the valley point is crossed, the tunnel diode obtains positive slope resistance. That is similar to the characteristics of a normal diode. So it behaves like a normal diode after beyond valley point.

Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.

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