Physics : Semiconductor Electronics: Materials, Devices and Simple Circuits

When a p-n diode is reverse biased,then

• no current flows

• the depletion region is increased

• the depletion region is reduced

• the height of the potential barrier is reduced

The circuit given below represents which of logic operations?

• AND

• NOT

• OR

• NOR

An amplifier  has a voltage gain A_v = 1000. The voltage gain in dB is

• 30 dB

• 60 dB

• 3 dB

• 20 dB

A light emitting diode (LED) has a voltage drop of 2 volt across it and passes a current of  10 mA when it operates with a 6 volt battery through a limiting resistor R. The value of R is

• 40 kΩ

• 4 kΩ

• 200 kΩ

• 400 kΩ

The minimum potential difference between the base and emitter required to switched a silicon transistor ON is approximately

• 1 V

• 3 V

• 5 V

• 4.2 V

Assertion: In common base configuration, the current gain of the transistor is less than unity. 

Reason: The collector terminal is reverse biased for amplification.

• If both assertion and reason are true and reason is the correct explanation of the assertion

• If both assertion and reason are true but reason is not the correct explanation of the assertion

• If assertion is true, but reason is false

• Both assertion and reason are false statements

Assertion:  A p-n junction with reverse bias can be used as a photo-diode to measure light intensity. 

Reason:  In a reverse bias condition the current is small but is more sensitive to changes in incident  light intensity.

• If both assertion and reason are true and reason is the correct explanation of the assertion

• If both assertion and reason are true but reason is not the correct explanation ofthe assertion

• If assertion is true, but reason is false

• Both assertion and reason are false statements

Which of the following logic gates is a universal gate?

• OR

• NOT

• AND

• NAND

Consider an n-p-n transistor amplifier in the common emitter configuration. The current gain of the transistor is 100. If the collector current changes by 1 mA, what will be the change in emitter current?

• 1.1 mA

• 1.01 mA

• 0.01 mA

• 10 mA

In a semiconductor material the mobilities of electrons and holes are μ_e and  μ_n respectively. Which of the following is true?

• μ_{e >} μ_n

• μ_e < μ_n

• μ_e = μ_n

• μ_e< 0 ;  μ_n > 0