Semi conductor devices practice · Medium

Assertion: For a conductor resistivity increases with increase in temperature.
Reason: Since $\rho=\frac{m}{n e^2 \tau}$, when temperature increases the random motion of free electrons increases and vibration of ions increases which decreases $\tau$.

Suppose a pure ${Si}$ crystal has $5 \times 10^{28}$ atoms ${m}^{-3}$. It is doped with $1 {ppm}$ concentration of pentavalent Arsenic. Calculate the number of holes formed. $\left(n_i=2.5 \times 10^{16} {~m}^{-3}\right)$.

In a transistor the collector current is always less than the emitter current because

The coordination number of body centred crystal is

To reduce the ripples in a rectifier circuit with capacitor filter
(a) $R_L$ should be increased.
(b) Input frequency should be decreased.
(c) Input frequency should be increased.
(d) Capacitors with high capacitance should be used.

If $\alpha$ and $\beta$ are the current gain in the $\mathrm{CB}$ and $\mathrm{CE}$ configurations respectively of the transistor circuit, then $(\beta-\alpha) / \alpha \beta=\ldots$.

Choose the correct statement about Zener diode

$n - p - n$ transistor are preferred to $p - n - p$ transistor because they have

A doped semiconductor has impurity levels $30 \mathrm{~meV}$ below the conduction band.

(a) Is the material n-type or p-type?

(b) In a thermal collision, an amount $k T$ of energy is given to the extra electron loosely bound to the impurity ion and this electron is just able to jump into the conduction band. Calculate the temperature $T$.

The average value of output direct current in a half wave rectifier is

A light-emitting diode ( $L E D$ ) has the voltage drop of $2 \mathrm{~V}$ across it and passes the current of $10 \mathrm{~A}$, when it operates with the $6 \mathrm{~V}$ battery with a limiting resistor ' $R$ '. What is the value of $\mathrm{R}$ ?

Number of secondary electrons emitted per number of primary electrons depends on

If a small amount of a trivalent atom is dropped with silicon crystal, then

In a common emitter amplifier the output signal receive across

For a constant collector-emitter voltage of $8 \mathrm{~V}$, the collector current of a transistor reached to the value of $6 \mathrm{~mA}$ from $4 \mathrm{~mA}$, whereas base current changed from $20 \mu \mathrm{A}$ to $25 \mu \mathrm{A}$ value. If transistor is in active state, small signal current gain (current amplification factor) will be

The incorrect statement about the property of a
Zener diode is:

Assertion : Transistor can be used as a switch.

Reason : Both linear & non-linear voltage bias dependence occurs in it.

On applying a potential of $- 1\;volt$ at the grid of a triode, the following relation between plate voltage ${V_p}\left( {volt} \right)$ and plate current ${I_p}$ (in $mA$) is found ${I_p} = 0.125{V_p} - 7.5$. If on applying $- 3\;volt$ potential at grid and $300\;V$ potential at plate, the plate current is found to be $5mA,$ then amplification factor of the triode is

When p-type semiconductor is heated, the number
of:

The nature of binding for a crystal with alternate and evenly spaced positive and negative ions is

In $p$-type semiconductors, conduction is due to

The fermi energy for a substance is

The correct relation between the two current gains $\alpha \;\mathrm{and}\;\beta$ in a transistor is

Diode is used as a/an

An experiment is performed to determine the I-V charactertitics of a Zener diode, which has a protective resistance of $R =100\Omega,$ and a maximum power of dissipation rating of $1 \Omega.$ The minimum voltage range of the DC source in the circuit is

Any digital circuit can be realised by repetitive use of only

Assertion: If the temperature of semiconductor is increases then its resistance decreases.

Reason: The energy gap between conduction band and valence band is small.

Statement-I: Germanium is preferred over silicon for making semiconductor devices.

Statement-II: Energy gap for Ge is more than that of ${Si}$.

Pure sodium $\left( {Na} \right)$ is a good conductor of electricity because the $3s$ and $3p$ atomic bands overlap to form a partially filled conduction band. By contrast the ionic sodium chloride $\left( {NaCl} \right)$ crystal is

Electrical conductivity of a semiconductor