regarding sensing circuit

[NARENDRA1234]

what is the use of base terminal in phototransistor circuit?

 

[Gagandeep sharma]

you have to mention the specific model no. of the type of reciever you are using.... !

 

[FvM]

you have to mention the specific model no

Why? The purpose of a base terminal, if exposed by a particular phototransistor, doesn't depend on the type. If you don't have a usage for it, you leave it unconnected. I guess, you'll find only a few application circuits that utilize it.

You can e.g.:
- connect the transistor as photodiode
- add a resistor to reduce the sensitivity
- add a capacitor to reduce the response bandwidth
- add a schottky clamp to speed up switching applications
- add feedback to form a bistable circuit

You can review manufacturer applications, if you'll find examples that use the base terminal.