ELECTRONIC DEVICES

Techno Test-2 Answer

Q.1) C

The open circuit voltage for a photo diode is given by

Voc  = eta*Vt ln(1+Iop/Io)
 
Io = reverse saturation current
Iop = optical current which is proportional to light intensity.
So, Voc increases logrithmically with light intensity.
 

Q.2) D

As only Si is an indirect band gap material so it cannot be used to make LED.

Q.3) C

Tunnel diode characteristics are shown below. In reverse bias the current varies linearly so it acts as a linear resister. Also it is highly doped (1 in 1000 atom) and has negative resistance  so it can be used in oscillators.

Tunnel

Q.4) A

The diode current is reversed and after some time it decays to zero. The diode voltage will be positive for some time and after that it becomes negative.

diode

Q.5) B

The width of the base region must be kept much lesser than diffusion length Ln of the electron so that the recombination in the base region is minimized.

 

Deja Vu

Q.1) C

Q.2) B

Q.3) B

Q.4) D

Q.5) B

Q.6) C