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PC817C Optocoupler IC — DIP-4, 5kV Isolation, 50–300% CTR, 35V Output (10-Pack)
PC817C Optocoupler IC DIP-4, 5kV Isolation, 50–300% CTR, 35V Output (10-Pack)
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PC817C Optocoupler — DIP-4, 5kV Isolation, 100–300% CTR, 35V Output (10-Pack)
The PC817C is a general-purpose phototransistor optocoupler in a DIP-4 through-hole package, providing 5,000V RMS galvanic isolation between input and output circuits. With a current transfer ratio (CTR) of 100–300% (Grade C), it is the most widely used optocoupler for SMPS feedback loops, PLC digital I/O isolation, and microcontroller-to-high-voltage circuit interfaces.
Key Specifications
| Parameter | Value |
|---|---|
| Package | DIP-4 (through-hole) |
| Isolation Voltage | 5,000V RMS |
| CTR Grade | C: 100–300% (at IF=5mA) |
| Output Collector Voltage (VCEO) | 35V |
| Forward Current (IF) | 50mA max |
| Collector Current (IC) | 50mA max |
| Response Time (tr/tf) | 4μs / 3μs typ. |
| Operating Temperature | -30°C to +100°C |
| Quantity | 10 pieces |
PC817 CTR Grade Guide
| Grade | CTR Range | Best For |
|---|---|---|
| A | 50–150% | Low-sensitivity circuits |
| B | 100–200% | General purpose |
| C | 100–300% | SMPS feedback (recommended) |
| D | 200–400% | High-sensitivity circuits |
Why Choose PC817C?
- Grade C (100–300% CTR) — optimal for SMPS feedback where consistent CTR is critical for stable regulation
- 5kV isolation — meets safety requirements for mains-connected and industrial circuits
- DIP-4 through-hole — easy to prototype on breadboard and replace in existing PCBs
- Industry-standard pinout — pin-compatible with EL817, LTV817, 4N35 (check datasheet)
- 10-pack value — sufficient for multiple builds and repair stock
Compatible With / Common Use Cases
- SMPS feedback: Flyback converter output voltage regulation loop (with TL431 shunt reference)
- PLC I/O isolation: 24V industrial signal to 3.3V/5V MCU input isolation
- Relay driver isolation: MCU GPIO to high-voltage relay coil drive
- AC zero-crossing detection: Mains voltage sensing for phase control circuits
- RS-232 / RS-485 isolation: Serial communication galvanic isolation
Frequently Asked Questions
Q: What is the difference between PC817A, PC817B, PC817C, and PC817D?
A: All are the same DIP-4 optocoupler with 5kV isolation — only the CTR (current transfer ratio) grade differs. Grade A: 50–150%, B: 100–200%, C: 100–300%, D: 200–400%. For SMPS feedback, Grade C is recommended for its balance of sensitivity and consistency.
Q: Can I replace PC817 with EL817 or LTV817?
A: Yes. EL817 (Everlight) and LTV817 (Lite-On) are direct pin-compatible replacements for PC817 (Sharp) with identical electrical specifications. Verify the CTR grade matches your circuit requirements.
Q: How do I calculate the input resistor for PC817 in an SMPS feedback circuit?
A: The LED forward voltage is ~1.2V at IF=5mA. For a 5V logic input: R = (5V − 1.2V) / 5mA = 760Ω, use 820Ω standard value. For 3.3V logic: R = (3.3V − 1.2V) / 5mA = 420Ω, use 470Ω.
Package Contents
- 10× PC817C Optocoupler IC (DIP-4)
