Phototransistor 3DU33

Phototransistor 3DU33

Phototransistor operation

• Photo transistors are operated in their active regime, although the base connection is left open circuit or disconnected because it is not required.
•  base of the photo transistor would only be used to bias the transistor so that additional collector current was flowing and this would mask any current flowing as a result of the photo-action.
• For operation the bias conditions are quite simple. The collector of an n-p-n transistor is made positive with respect to the emitter or negative for a p-n-p transistor.
• light enters the base region of the phototransistor where it causes whole electron pairs to be generated. This mainly occurs in the reverse biased base-collector junction.
• hole-electron pairs move under the influence of the electric field and provide the base current, causing electrons to be injected into the emitter.

Specification 

• Material: Silicon
• Reverse Breakdown Voltage: 15 VDC
• Maximum Working Voltage: 10 VDC
• Dark Current: 0.3 μA
• Light Current: 0.5 – 1 mA