Question

1) a) Compare pin photodiode with pn junction photodiode. Please write one application best for each pin and pn photodiode with a reason.

b) For a photodiode of depletion layer 20 micrometer and relative dielectric constant 4 and area of 0.005 mm2 calculate the depletion layer capacitance and time constant for 50 ohm resistor.

Answer 1

b)Depletion layer capacitance,

CT=KA/W

Where K= relative dielectric constant, A=area, W= width of depletion region.

CT = 4 *0.005 * 10^-6/ 20 * 10^-6

CT=0.001

Time constant = 1/RC

= 1/50*0.001= 20ohm-1 F-1