Following are the difference between PN junction diode and Photo diode:
| PN junction diode | Photo diode |
|---|---|
| The PN junction diode is operated in forward biased mode. | The photo diode is operated in reverse biased mode. |
| It is made up of either Germanium or silicon. | It is made up of silicon. |
| The forward current is proportional to forward biased voltage. | The reverse current is proportional to light intensity. |
| It is used as rectifier, clamper, clipper, voltage multiplier etc. | It is used in photo detector, camera, light intensity meter, optocoupler etc. |
The circuit symbol is
 PN junction diode |
The circuit symbol is
 Photo diode |