mockboard pt.3

At very high temperatures the extrinsic semiconductors become intrinsic because

• drive in diffusion of dopants and carriers
• band to band transition dominants over impurity ionization
• impurity ionization dominants over band to band transition
• band to band transition is balanced by impurity ionization

To forward-bias a diode,

• the anode voltage must be positive with respect to its cathode.
• the anode voltage must be negative with respect to its cathode.
• the cathode voltage must be positive with respect to its anode.
• Either A or B.

When a voltage is applied to a semiconductor crystal then the free electrons will flow.

• towards positive terminal
• towards negative terminal
• either towards positive terminal or negative terminal
• towards positive terminal for 1 μs and towards negative terminal for next 1 μs

A diode is a

• unidirectional device.
• linear device
• nonlinear device
• Both A and C.

Avalanche voltage is routinely exceeded when a P-N junction acts as a:

• Current rectifier
• Variable resistor
• Variable capacitor
• Voltage regulator

Of the following, which material allows the lowest forward voltage drop in a diode?

• Selenium
• Silicon
• Copper
• Germanium

A semiconductor, such as silicon, has an electron valence of

• ±4.
• – 7.
• + 1.
• 0.

Assertion (A): The reverse saturation current in a semiconductor diode is 4nA at 20°C and 32 nA at 50°C. Reason (R): The reverse saturation current in a semiconductor diode doubles for every 10°C rise in temperature.

• Both A and R are true and R is correct explanation of A
• Both A and R are true but R is not a correct explanation of A
• A is true but R is false
• A is false but R is true

Determine the diode current at 20 oC for a silicon diode with reverse saturation current of 50 nA and an applied forward bias of 0.6 V.

• 9.17 mA
• 7.19 mA
• 1.79 mA
• 9.7 mA

A disadvantage of gallium-arsenide devices is that:

• The charge carriers move fast
• The material does not react to ionizing radiation.
• It is expensive to produce
• It must be used at high frequencies