PC817 Transistor Output Optocoupler DIP-4

PC817 Transistor Output Optocoupler DIP-4 is a fundamental and widely used component that provides critical electrical isolation between two circuits. This optocoupler integrates an infrared Light Emitting Diode (LED) on the input side and a phototransistor on the output side. Consequently, it transmits signals using light instead of direct electrical connection. The PC817 effectively separates low-voltage control circuits (like microcontrollers) from high-voltage or noisy power circuits, preventing ground loops and transient spikes from damaging sensitive electronics. Therefore, designers frequently employ this device in power supplies, signal transmission systems, and motor control applications where safety and signal integrity are paramount. Furthermore, its simple 4-pin configuration ensures straightforward integration into countless designs.

Key Features:

• High Isolation Voltage: The device offers a high insulation voltage, typically 5000 V_RMS, providing superb safety separation between input and output.
• Low Input Current: The input LED requires a low forward current, making it easy to drive directly from standard digital logic families (TTL, CMOS).
• Transistor Output: The NPN phototransistor output allows for both DC and low-frequency AC signal switching, offering flexibility in circuit design.
• High Current Transfer Ratio (CTR): The PC817 offers a respectable CTR range, ensuring that a small input current effectively drives the output transistor into saturation.
• Standard DIP-4 Package: The ubiquitous 4-pin Dual In-line Package simplifies mounting and ensures compatibility with standard PCBs and breadboards.

Technical Specifications:

• Isolation Voltage (V_ISO): 5000 V_RMS minimum
• Collector-Emitter Voltage (V_CEO): 80 V maximum
• Collector Current (I_C): 50 mA maximum
• Forward Current (I_F): 50 mA maximum (Input LED)
• Current Transfer Ratio (CTR): 50% to 600% (depending on specific bin/suffix)
• Rise/Fall Time (t_r / t_f): Typically ≈ 4 μs at I_C=2 mA
• Operating Temperature Range: −30°C to +100°C

Mechanical Specifications:

• Package Type: DIP-4 (Through-Hole)
• Mounting: Through-Hole Technology (THT)
• Material: Plastic Molded Case (Epoxy Resin)
• Flammability Rating: UL 94 V-0

Dimensions:

• Body Length: ≈ 4.6 mm
• Body Width: ≈ 4.5 mm
• Pin Pitch (Between pins): 2.54 mm (0.1 inch)
• Row Spacing (Between rows): 4.58 mm minimum
• Lead Material: Tinned Copper

Pinout and Wiring:

• Pin 1 (Anode): Connect to the positive power supply of the input circuit via a current-limiting resistor.
• Pin 2 (Cathode): Connect to the microcontroller’s GPIO pin or ground (GND) to activate the LED and transmit the signal.
• Pin 3 (Emitter): Connect to the ground (GND) of the output circuit. This terminal is the transistor’s common connection.
• Pin 4 (Collector): Connect to the positive voltage supply of the output circuit via a pull-up resistor (R_L). This is the switching output.

Datasheet Reference:

• Download Sharp PC817 Optocoupler Datasheet

Commonly Used in:

• Switching Power Supplies: Designers utilize the PC817 for feedback loops to maintain voltage regulation while preserving isolation.
• Digital Interfacing: It effectively interfaces between systems using different voltage levels (e.g., 3.3V logic to 12V or 24V industrial signals).
• Microcontroller Isolation: Engineers frequently use the device to protect sensitive microprocessors from external noise or power surges.

Applications:

• AC/DC Power Regulation: The optocoupler controls feedback in flyback and forward converters to isolate the control circuit.
• Data Communications: It protects data lines, ensuring isolated signal transmission between peripherals and the main system.
• Motor Control Circuits: Consequently, it provides the necessary isolation when driving MOSFETs or IGBTs used in motor drive stages.
• Solid State Relays (SSRs): The PC817 often forms the input stage of many low-power solid-state relay designs.

Equivalent Models:

• EL817 (Everlight): This is perhaps the most common direct functional replacement for the PC817, offering identical specifications.
• LTV-817 (Lite-On): A highly popular cross-reference part number that shares the same electrical and mechanical properties.
• SFH615A (Vishay): However, this is a similar general-purpose optocoupler often used as a substitute, sometimes offering tighter CTR bins.

Package Includes:

• 1 x PC817 Transistor Output Optocoupler DIP-4