# PC817

**Sharp** · Phototransistor optocoupler · DIP-4

General-purpose photocoupler pairing an infrared LED (IRED) with an NPN phototransistor across a 5.0 kVrms isolation barrier, in a 4-pin DIP package. It transfers a logic signal while keeping the two sides galvanically isolated, protecting an MCU from a high-voltage or noisy domain. Drive the input LED through a series resistor (~10 mA); the output transistor pulls a pulled-up line low. The default cheap isolator for feedback, triggers, and level domains.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | ANODE | passive | Anode of the input-side infrared LED (IRED). Drive with forward current I_F (typical operating 5 mA, absolute max 50 mA DC / 1 A peak, 100 us / 0.001 duty). Forward voltage V_F ~= 1.2 V typ (1.4 V max) at I_F = 20 mA. Use a series resistor to limit current. |
| 2 | CATHODE | passive | Cathode of the input-side infrared LED. Return path for the LED forward current; reverse voltage V_R rated 6 V max. Typically tied to the input-side ground/return. |
| 3 | EMITTER | passive | Emitter of the output-side NPN phototransistor. Usually tied to the output-side ground (common-emitter) or drives a load in common-collector configuration. Rated V_ECO = 6 V. |
| 4 | COLLECTOR | passive | Collector of the output-side NPN phototransistor. Photocurrent flows here when the input LED is driven; conducts to the emitter in proportion to LED current per the CTR (50-600% at I_F = 5 mA, V_CE = 5 V). V_CEO = 80 V, I_C = 50 mA max, V_CE(sat) = 0.1 V typ (0.2 V max) at I_F = 20 mA, I_C = 1 mA. |

## Key specifications

| Parameter | Value |
|---|---|
| Type | Phototransistor optocoupler |
| Isolation voltage | 5.0 kVrms |
| Input | Infrared LED (Vf ~1.2 V, IF 50 mA max) |
| Output | NPN phototransistor (VCEO 35 V, IC 50 mA) |
| Current transfer ratio (CTR) | 50-600% (ranked) |
| Isolation | Galvanic input-to-output |
| Package | DIP-4 |
| Body (L×W×H) | 6.5 × 4.6 × 3.5 mm |

## Ordering variants

Same part, different packaging or reel option.

- `PC817X (DIP-4)`
- `PC817C (DIP-4, CTR rank C)`

## CAD (KiCad official)

- Symbol: `Isolator:PC817`
- Footprint: `Package_DIP:DIP-4_W7.62mm`
- 3D model: DIP-4 (KiCad packages3D)
- 3D model files: `pc817-etched.step` / `pc817-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `pc817.step` / `pc817.glb` are the bare package body.

## Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

- **Datasheet:** [Sharp datasheet](https://www.farnell.com/datasheets/73758.pdf) (15 pp, sha256 `a485f78cde6091c8`, retrieved 2026-08-17, tier: cse)
- **Extractor:** `ds2sf` (Claude) — every pin and dimension is cited to a datasheet page; refuses to fabricate.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/pc817-datasheet.pdf)