Part Number: FOD817BSD

Manufacturer: onsemi


Shipped from: Shenzhen/HK Warehouse

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Technical Specifications of FOD817BSD

Datasheet  FOD817BSD datasheet
Category Isolators
Family Optoisolators – Transistor, Photovoltaic Output
Manufacturer Fairchild Semiconductor
Packaging Tape & Reel (TR)
Part Status Active
Number of Channels 1
Voltage – Isolation 5000Vrms
Current Transfer Ratio (Min) 130% @ 5mA
Current Transfer Ratio (Max) 260% @ 5mA
Turn On / Turn Off Time (Typ)
Rise / Fall Time (Typ) 4μs, 3μs
Input Type DC
Output Type Transistor
Voltage – Output (Max) 70V
Current – Output / Channel 50mA
Voltage – Forward (Vf) (Typ) 1.2V
Current – DC Forward (If) (Max) 50mA
Vce Saturation (Max) 200mV
Operating Temperature -55°C ~ 110°C
Mounting Type Surface Mount
Package / Case 4-SMD, Gull Wing
Supplier Device Package 4-SMD

FOD817BSD Introduction

The FOD817BSD is an important part of electronic systems that have to do with isolating and sending signals. It is made by Onsemi and is part of the FOD814 and FOD817 lines of optocouplers or optoisolators. These devices use a combination of infrared-generating diodes and silicon phototransistors to keep electrical signals separate and send them quickly. In this detailed guide, we’ll go over the FOD817BSD and its related series’ features, how they work, and how they can be used. This will give you a solid idea of how they work.

Overview of Optocouplers

● What are Optocouplers?

Optocouplers, often referred to as opt isolators or photocouplers, are electronic components that offer electrical isolation between two circuits while still permitting the flow of signals or power. They are made up of two sides—an input side and an output side—that are physically separated by an optically transparent barrier, usually a gap or an insulating substance.

The light-emitting diode (LED) that typically makes up the input side of an optocoupler generates light when current flows across it. The light emitted by the LED is detected by a light-sensitive component on the output side, such as a phototransistor or a photodiode, which produces an electrical signal proportional to the light intensity.

Isolation in electronic circuits is important. In order to avoid unwanted electrical interactions between various components or subsystems, isolation is essential in electronic circuits. As a result, safety is improved, signal integrity is improved, noise interference is decreased, and sensitive electronics are protected from excessive voltages or surges. When signals must be transmitted across various voltage domains or when there are variations in the ground potential, isolation is crucial.

Optocouplers’ Function in Isolation In order to provide electrical separation in electronic circuits, optocouplers are essential. Direct electrical connections are not required since they employ light instead to transmit signals or power across the isolation barrier. The output side of the optocoupler, which has a light-sensitive component, receives light pulses created when an input signal is supplied to the LED side of the optocoupler.

The input signal modulates the light that the LED emits, allowing information or power to be sent without a direct electrical connection between the input and output circuits. With the help of this optical coupling, the optocoupler is effectively isolated from electrical noise, voltage spikes, and ground potential changes on one side of the device.

Numerous applications, such as industrial automation, power electronics, telecommunications, medical devices, and more, utilize optocouplers extensively. They provide dependable and effective isolation, allowing complicated electronic systems to transmit signals safely and precisely.

Components and Configuration

A specific series of optocouplers called the FOD817 series uses a silicon phototransistor driven by a gallium arsenide infrared emitting diode (LED) in a 4-pin dual in-line package (DIP). Four pins are included in the packaging, and they are normally labeled as follows:

  • Pin 1: Anode (A)
  • Pin 2: Cathode (K)
  • Pin 3: Collector (C)
  • Pin 4: Emitter (E)

The FOD817BSD, in particular, is a variant within the FOD817 series and could differ in some ways from other models in the series in terms of electrical characteristics or performance parameters. For exact information regarding the FOD817BSD, please refer to the datasheet or product documentation.

When a forward current is provided, the gallium arsenide infrared emitting diode is what produces the infrared light. The silicon phototransistor on the output side then takes in this light.

FOD817BSD Working Principle

The modification of light generated by the LED and its detection by the phototransistor form the foundation of the FOD817 series’ operation. Here is a step-by-step explanation of the basic idea:

Input Side (LED)

  • The LED emits infrared light when a forward current is applied to its anode (A) and cathode (K).
  • The forward current passing through the LED has a direct relationship with the brightness of the light that is emitted.

Optical Coupling

  • On the output side, the phototransistor receives the LED’s light that is being emitted.
  • A physically separate, optically clear wall within the package separates the LED and phototransistor from one another.

Output Side (Phototransistor)

  • The phototransistor takes in the light that the LED emits.
  • The phototransistor is stimulated by the incident light, which causes it to conduct current.
  • The phototransistor’s current varies in direct proportion to the brightness of the light it receives.

Electrical Output

  • An electrical output signal is produced by the current passing through the phototransistor’s collector (C) and emitter (E) pins.
  • The optocoupler’s input side may receive feedback from this output signal or be driven by it.

The FOD817 series offers electrical separation between the input and output sides of the optocoupler by utilizing the optically coupled LED and phototransistor. It efficiently moves signals or power while preserving isolation, safeguarding delicate components, cutting down on noise interference, and improving system performance as a whole.

Frequently Asked Questions (FAQs)

What is the difference between the FOD814 and FOD817 series?

The FOD814 and FOD817 series have different configurations and components. The FOD814 series utilizes two gallium arsenide infrared emitting diodes connected in inverse parallel to effectively drive an output silicon phototransistor. This configuration enables the transmission of signals in both directions.

In contrast, the FOD817 series utilizes a single gallium arsenide infrared emitting diode to drive a silicon phototransistor for unidirectional signal transmission. It’s important to note that different models within each series may have specific performance requirements and electrical characteristics.

Can the FOD817BSD be used in areas with high temperatures?

The FOD817BSD’s specified operating temperature range, as provided in the datasheet, determines whether it is suitable for high-temperature situations. To ensure dependable performance and lifespan, optocouplers—including the FOD817BSD—are designed to work within specific temperature ranges.


In conclusion, the FOD814 and FOD817 series optocouplers provide valuable benefits, including electrical isolation and efficient signal transfer. These components, which integrate gallium arsenide infrared emitting diodes and silicon phototransistors in a 4-pin dual in-line package, have a wide range of applications in various industries. They are used to ensure safety, maintain signal integrity, and protect sensitive circuitry.

When incorporating these optocouplers into your designs, it is important to carefully consider their electrical characteristics, mechanical specifications, and thermal management. You can achieve reliable isolation, accurate signal transmission, and enhanced system performance by utilizing the capabilities of the FOD814 and FOD817 series. If you are looking to source the FOD817BSD and want to explore additional options, please contact us at ICRFQ. We are a trusted supplier based in China.

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