Electronics and Communication Engineering - Electronic Devices and Circuits

36.
For BJT transistor. The maximum power dissipation is specified as 350 mW if ambient temperature is 25°C. If ambient temperature is 60°C the maximum power dissipation should be limited to about
100 mW
250 mW
450 mW
600 mW
Answer: Option
Explanation:

350 - 2.5 (60 - 25) ∼ 250 mW.


37.
The concentration of minority carriers in a semiconductor depends mainly on
the extent of doping
temperature
the applied bias
none of the above
Answer: Option
Explanation:

Minority carriers are generated due to thermal excitation.


38.
Which of the following has highest conductivity?
Silver
Aluminium
Tungsten
Platinum
Answer: Option
Explanation:

Silver has highest conductivity (and lowest resistivity) in all metals.


39.
In a bipolar junction transistor the base region is made very thin so that
recombination in base region is minimum
electric field gradient in base is high
base can be easily fabricated
base can be easily biased
Answer: Option
Explanation:

Since recombination in base region is minimum, I - IE.


40.
Compared to bipolar junction transistor, a JFET has
lower input impedance
high input impedance and high voltage gain
higher voltage gain
high input impedance and low voltage gain
Answer: Option
Explanation:

JFET is voltage controlled device. Therefore its input impedance is high. But voltage gain is lower than in BJT.