# modify the optocoupler that use NPN t

#### mermaid09

Joined Nov 21, 2009
9
Hai everyone...im looking to modify the optocoupler that use NPN transistor like in below diagram.

My aim is to modify above circuit to become optocoupler that same funtion as optocoupler that use phototransistor. My question here is
- if the base of NPN transistor in not to connect to any compenent(opened based), are there same function like photoransistor?
- if yes, i want to build the above circuit ( at part NPN transistor) to become darlintong circuit without use the base pin at pin 6. Then what suitable transistor that i should choose?i will use 12 V DC supply voltage to darlington circuit.

TQ..

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#### hgmjr

Joined Jan 28, 2005
9,029
Is your goal to modify a simulation model or are you wanting to modify actual circuitry?

Under most circumstances, you can leave the base unconnected.

hgmjr

tq for reply..im only to modify a simulation model..then i dont know how to choose the correct type of transistor to become as darlington circuit. I dont know what type of the transistor that use in the internal diagram, so i cant match the transistor.