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)

Provenance

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

Datasheet: Sharp datasheet (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