Match the given lists : Codes :List – I (Name of the Device) List – II (Application) a. Diode i. Rectification b. Tunnel diode ii. Microwave switching c. Zener diode iii. An oscillator d. PIN diode iv. Voltage regulation
a-i, b-iii, c-iv, d-ii
Each device is defined by one property, and that property names its application: a-i, b-iii, c-iv, d-ii — option 1.
| Device | Distinctive property | Application |
|---|---|---|
| a. Diode | Conducts one way only | i. Rectification |
| b. Tunnel diode | Negative differential resistance | iii. Oscillator |
| c. Zener diode | Constant voltage in breakdown | iv. Voltage regulation |
| d. PIN diode | Bias-controlled linear resistance at RF | ii. Microwave switching |
b — why negative resistance makes an oscillator. Both sides of a tunnel diode's junction are doped degenerately, so the depletion layer is only about 10 nm across and carriers tunnel straight through at small forward bias. As the bias rises further the occupied states on one side stop lining up with empty states on the other, the tunnelling window closes, and current falls while voltage rises:
\(\dfrac{dI}{dV}\lt0\ \text{between}\ V_{P}\ \text{and}\ V_{V}\)
Placed across a tuned circuit, that negative resistance cancels the circuit's positive loss resistance, so an oscillation once started neither decays nor needs any feedback path. Because tunnelling has essentially no transit delay, it works into the tens of gigahertz.
c — why the zener regulates. In breakdown its characteristic is almost vertical: a large change of current produces a very small change of voltage, so the dynamic resistance
\(r_{z}=\dfrac{\Delta V}{\Delta I}\)
is only a few ohms. Fed through a series resistor, it absorbs whatever current the load does not take and holds the voltage across itself constant.
d — why the PIN switches. Its thick intrinsic layer stores charge for hundreds of nanoseconds, so above about 1 MHz that charge cannot follow the RF cycle. The diode stops rectifying and becomes a linear resistor whose value is set by the DC bias — a fraction of an ohm forward, kilohms reverse. Being linear, it introduces no distortion, which is precisely what a microwave switch or attenuator requires.
Note how b and d are complementary : the tunnel diode is prized for a strong non-linearity, the PIN diode for the absence of one, and each application follows from that single fact.
Hence, the correct code is a-i, b-iii, c-iv, d-ii.
Similar Questions
A PIN diode can not be used as
i. Microwave switch
ii. Microwave mixer
iii. Microwave detectorWhich is correct ?
________ diode is not used as a microwave mixer or detector.
Varacter diodes have the following properties :
A. Junction capacitance varies with bias voltage
B. Junction capacitance varies with time
C. Non linearity of varacter diodes makes them suitable for frequency multipliers
D. Linearity of varactor diode makes them suitable for frequency multipliers.
Choose the correct answer from the options given below:
In a tunnel diode, the degeneracy on the n-side can be expressed as
The static current voltage characteristics of a tunnel diode consist of
(a) Tunneling current and thermal current
(b) Thermal current and excess current
(c) Tunneling current only
(d) Tunneling current, excess current and thermal current
Out of these which are correct ?
Match the following :
List – I List – II a. Gunn diode i. degenerate silicon b. Tunnel diode ii. n-type Ga As c. BJT iii. Silicon d. Diode (P-N junction) iv. \(I_o\left[\exp\left(\dfrac{qV}{kT}\right)-1\right]\) Choose the correct answer from the codes given below:
A TRAPATT diode has the doping concentration NA = 2 x 1015/cm3 and a current density of 20 kA/cm2. The value of avalanche zone velocity is given by :
Assertion (A) : The Gunn diode characteristics shows the region of negative resistance.
Reason (R) : The Gunn diode is made of n-type and p-type degenerate semiconductor.
Select your answer using the codes given below.
Which of the following statements are correct for Tunnel Diode ?
(a) 1 impurity atom in 103 atoms
(b) Very high doping in both p and n regions
(c) 1 impurity atom in 108 atoms
(d) used as a voltage controlled devices
Out of the above, the following is the correct answer :
Which of the following statements are true for a zener diode ?
(a) The voltage across the zener resistance is zero.
(b) The diode is used as a constant voltage device.
(c) The diode is used as a varactor diode.
(d) The diode is formed of heavily doped p and n-type semiconductor.
Options :
Important Questions from Types of Diode
A PIN diode can not be used as
i. Microwave switch
ii. Microwave mixer
iii. Microwave detectorWhich is correct ?
________ diode is not used as a microwave mixer or detector.
Varacter diodes have the following properties :
A. Junction capacitance varies with bias voltage
B. Junction capacitance varies with time
C. Non linearity of varacter diodes makes them suitable for frequency multipliers
D. Linearity of varactor diode makes them suitable for frequency multipliers.
Choose the correct answer from the options given below:
In a tunnel diode, the degeneracy on the n-side can be expressed as
The static current voltage characteristics of a tunnel diode consist of
(a) Tunneling current and thermal current
(b) Thermal current and excess current
(c) Tunneling current only
(d) Tunneling current, excess current and thermal current
Out of these which are correct ?
