State advantages and disadvantages of photodiode.

Answer: Advantages — quick response, low noise, low cost and small size, can work at high frequency (long life, no high voltage needed). Disadvantages — small current output that needs amplification, temperature dependent dark current, needs a reverse bias and its response depends on the wavelength of light.

Advantages:

1. Very quick response (switching between on and off is fast), so it works at high frequencies.
2. Low noise, low cost, small and light; long life.
3. Output current varies linearly with the intensity of light, useful for light measurement.

Disadvantages:

1. The photocurrent is very small (microampere range), so an amplifier is usually needed.
2. The dark (reverse saturation) current increases with temperature, so it is temperature dependent and less stable.
3. It needs an external reverse bias and has a small active area; its sensitivity depends on the wavelength of the incident light.