FL817 Datasheet – Phototransistor – Fang jing

Part Number : FL817


Package : DIP 4 Pin

Manufacutures : Fang Jing



The FL817 is an optocoupler or optoisolator device. Optocouplers are electronic components that consist of an infrared light-emitting diode (LED) and a phototransistor or photodiode within a single package. They are used to electrically isolate or couple two circuits while allowing them to communicate optically.

The FL817 specifically is a popular optocoupler that provides electrical isolation between an input and output circuit. It typically consists of an infrared LED on the input side and a phototransistor on the output side. When current is applied to the LED, it emits light, which is then detected by the phototransistor, causing it to conduct current. This way, the input and output sides of the FL817 are electrically isolated, meaning they are physically separated and do not share a common ground.


1. Current transfer ratio (CTR:MIN.50% at IF =5mA ,VCE =5V)
2. High isolation voltage between input and output (Viso=5000 V rms )
3. Compact dual-in-line package
4. Pb free



FL817 data sheet

Options available

1. Leads with 0.4”(10.16mm) spacing (M Type)
2. Leads bends for surface mounting (S Type)
3. Tape and Reel of TypeⅠ for SMD(Add”-TA” Suffix)
4. Tape and Reel of TypeⅡ for SMD(Add”-TB” Suffix)
5. The tape is 16mm and is wound on a 33cm reel



• Computer terminals
• System appliances, measuring instruments
• Registers, copiers, automatic vending machines
• Cassette type recorder
• Electric home appliances, such as fan heaters, etc.
• Signal transmission between circuits of different potentials and impedances

(1) Isolation in control systems: It can be used to isolate high-voltage or noisy control signals from microcontrollers, PLCs (Programmable Logic Controllers), or other sensitive components.

(2) Switching applications: It can be used to control high-power devices, such as relays or power transistors, where electrical isolation is required to protect the control circuitry.

(3) Communication interfaces: It can be used in serial communication interfaces, such as RS-232 or USB, to provide isolation between the computer or controller and external devices.

(4) Power supply feedback: It can be used to provide feedback and control signals in power supply circuits while maintaining isolation between the high-voltage side and low-voltage control circuitry.


FL817 Data Sheet