Specs side by side
2 parts compared · 3 differing specs across 5 total parameters.
| Parameter | ||
|---|---|---|
| Case | DIP-6 | DIP-4 / SMD-4 |
| Component Category | Phototransistor Optocouplers (6-pin) | Phototransistor Optocouplers |
| Market Reality | The 4N2x / 4N3x row is the general-purpose opto that predates the PC817 and still fills industrial boards, instruments and old audio gear: a 6-pin DIP with an infrared LED, a phototransistor, and one extra pin the 4-pin generation gave up - the base of the phototransistor, brought out for speed-up tricks and threshold trimming. The family is a CTR ladder wearing four part numbers: 4N25/26 at 20% minimum, 4N27/28 at 10%, and the 4N35/36/37 trio at 100% - one of the highest CTRs of any general-purpose opto, which is why it survives in circuits that need gain more than speed. Substituting within the row is honest work; substituting against the 4-pin PC817 row is the classic socket error. | The PC817 is the optocoupler of SMPS feedback loops and low-speed isolation across every price class of equipment - one of the highest-volume optos ever made. Genuine supply is continuous, but the part is a specification, not a single part number: the CTR rank (A / B / C / D or combined bins) and the isolation class decide whether a substitute works, and the second-source universe (LTV-817, EL817, TLP521-1, HCPL-817) is enormous precisely because designers treat the function as generic. The buying question is always which rank and which vendor, not whether the part exists. |
| Role In Circuit | Original Reference Part | Original Reference Part |
| Sourcing Status | Active Shenzhen Spot Sourcing (24–48h) | Active Shenzhen Spot Sourcing (24–48h) |
Parts
- 4N35 / 4N25 · onsemi
- PC817 · sharp