81.

A p-type material is electrically

• positive

• negative

• neutral

• depends on the concentration of p impurities

Let n_e and n_h represent the number density of electrons and holes in a semiconductor. Then

• n_e > n_h  if the semiconductor is intrinsic 

• n_e < n_h  if the semiconductor is intrinsic 

• n_e ≠ n_h, if the semiconductor is intrinsic 

• n_e = n_h, if the semiconductor is intrinsic 

In a n-p-n transistor amplifier, the collector current is 9 mA. If 90% of the electrons from the emitter reach the collector, then

• α = 0.9, β = 9.0

• the base current is 10 mA

• the emitter current is 1 mA

• α = 9.0, β = 0.9

In a properly biased transistor

• both depletion layers are equally large

• both depletion layers are equally small

• emitter-base depletion layer is large but base-collector depletion layer is small

• emitter-base depletion layer is small but base-collector depletion layer is large.

A semiconductor has an electron concentration of 8 x 10¹³ /m³ and hole concentration of 5.5 10¹²/m³. The semiconductor is

• n-type

• p-type

• intrinsic semiconductor

• p-n junction

In the figure shown below, which of the diodes are forward biased ?

• 1, 2, 3

• 2, 4, 5

• 1, 3, 4

• 2, 3, 4

Given below are four logic gate symbols . Those for OR, NOR and NAND are respectively

• 1, 4, 3

• 4, 1, 2

• 1, 3, 4

• 4, 2, 1

The electrical circuit used to get smooth DC output from a rectifier circuit is called

• filter

• oscillator

• logic gates

• amplifier

In the case of constants α and β of a transistor

• α = β

• β < 1, α > 1

• αβ = 1

• β > 1, α < 1

The emitter-base junction of a transistor is ............ biased while the collector-base junction is ......... biased.

• forward, forward

• forward, reverse

• reverse, forward

• reverse, reverse