Photodiode

Q. In a PN junction photo cell, the value of photo-electromotive force produced by monochromatic light is proportional to

1. The voltage applied at the PN junction
2. The barrier voltage at the PN junction
3. The intensity of the light falling on the cell
4. The frequency of the light falling on the cell

Q. A p-n photodiode is fabricated with a semiconductor having band gap of 3 $ev$, then

1. It can detect $\lambda =500nm$
2. It cannot detect $\lambda =300nm$
3. It can detect $\lambda =240nm$
4. It cannot detect $\lambda =400nm$

Q. A photo diode measures ....... of light and is always operated in ........ biased configuration.

1. frequency, reverse
2. intensity, forward
3. frequency, forward
4. intensity, reverse

Q. In a PN junction photo cell, the value of photo-electromotive force produced by monochromatic light is proportional to

1. The frequency of the light falling on the cell
2. The voltage applied at the PN junction
3. The barrier voltage at the PN junction
4. The intensity of the light falling on the cell

Q. A photodiode has two p-n junctions.

1. False
2. True

Q.

In a photodiode, the conductivity increases when the material is exposed to light. It is found that the conductivity changes only if the wavelength is less than 620 nm. What is the band gap ?

Q.

The plate current, plate voltage and grid voltage of a 6F6 triode tube are related as
$i_p=41(V_p+7V_g{)}^{1.41}$
Where $V_p$ and $V_g$ are in volts and $i_p$ in microamperes. The tube is operated at $V_p=250V,V_g=-20V.$ Calculate (a) The tube current (b) the plate resistance, (c) the mutual conductance and (d) the amplification factor.

Q. A p-n photodiode is fabricated from a semiconductor with band gapof 2.8 eV. Can it detect a wavelength of 6000 nm?

Q. Why should a photodiode be operated in reverse biased mode?

Q. A man wants to measure current $\sim mA$. He should use

1. photo multiplier tube
2. photo multiplier tube and amplifier
3. photo cell and amplifier
4. photo cell and two stage amplifier