Match the following : Choose the correct answer from the codes given below: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. \(I_o\left[\exp\left(\dfrac{qV}{kT}\right)-1\right]\)
a-ii, b-i, c-iii, d-iv
Three of the four entries name a material and one gives an equation, so the equation pairs itself first and the rest follow from what each device is made of.
a → ii. Gunn diode — n-type GaAs. The Gunn effect is not a junction effect at all; it needs a bulk semiconductor with a particular band structure, one having a low-energy central valley and a nearby satellite valley of higher effective mass. Electrons transferred to the upper valley become heavier and slower, so the drift velocity falls as the field rises — bulk negative differential resistance. Gallium arsenide (and InP) have that two-valley structure; silicon does not, which is why a Gunn diode cannot be made from it.
b → i. Tunnel diode — degenerate silicon. The word degenerate is the giveaway: both sides are doped so heavily (1019–1020 cm−3) that the Fermi level enters the bands and the junction becomes only ~10 nm wide, thin enough for electrons to tunnel through.
c → iii. BJT — silicon. The ordinary bipolar transistor is the classic silicon device; nothing exotic is required.
d → iv. P-N junction diode — the Shockley equation.
\(I=I_o\left[\exp\left(\dfrac{qV}{kT}\right)-1\right]\)
which describes the exponential rise in forward bias and the saturation at −Io in reverse.
The quickest route through the question. Pair d with iv immediately, since it is the only equation. Then note that "degenerate silicon" can only describe the tunnel diode — degeneracy is its defining feature — leaving plain "silicon" for the BJT and n-type GaAs for the Gunn diode. Two independent deductions settle all four.
Hence, the correct matching is a-ii, b-i, c-iii, d-iv.
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.
Match the given lists :
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 Codes :
An important figure of merit for microwave application of Schottky diode is forward bias cut off frequency fco and is given by :
Assertion (A) : A tunnel diode consists of simple p-n junction mode of degenerate semiconductor. The current voltage characteristics consists of three components and shows the negative differential region over part of the forward characteristics.
Reason (R) : In tunnel diode the p-side is highly doped and n-side is highly doped and also used as 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 ?
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.
Important Questions from Types of Diode
For which of the following diodes when the voltage is increased the current flowing through it decreases?
Which of the following is the main application of Zener diode?
A tunnel diode is
When we tune in any desired station in a radio receiver by rotating the tuning control we vary
Which diode is used as a voltage regulator?
