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onsemi 4N25 — Optoisolators

4N25 Optoisolator – onsemi, 5300Vrms, 6-DIP, Obsolete

MPN4N25
Obsolete

onsemi 4N25, 1-channel optoisolator, DC input, transistor with base output, 5300Vrms isolation, 6-DIP (0.300", 7.62mm) through-hole package, -55°C to 100°C operating range.

$0.6100Ref. price · indicative, final on quote
onsemi 4N25 datasheet (PDF)
Packaging6-DIP (0.300", 7.62mm)
RoHSROHS3 Compliant
Independent supplier — new & surplus stockAuthenticity-screened · ESD-safe packingListing updated Jul 2026

Specifications

4N25 specifications
ParameterValue
Input typeDC
Output typeTransistor with Base
MountingThrough Hole
Voltage - isolation5300Vrms
Voltage - output30V
Voltage - forward (Vf)1.18V
Current transfer ratio20% @ 10mA
Current - DC forward (If)100 mA
Operating temperature-55°C ~ 100°C
PackageTube
Case6-DIP (0.300\", 7.62mm)
Channels1
Vce saturation500mV
Turn on (Turn off time)2µs, 2µs

Product details

5300Vrms isolation in a through-hole 6-DIP

The onsemi 4N25 is a single-channel optoisolator with a DC input LED and a phototransistor output that brings the base terminal out. The 5300Vrms isolation rating is the headline spec — it qualifies the part for basic isolation in mains-referenced circuits, motor drives, and industrial PLC I/O where galvanic separation between control and power domains is non-negotiable.

20% minimum CTR and 2µs switching

Minimum current transfer ratio is 20% at 10 mA forward current. That floor sets the load resistor ceiling: with a 30V output rating and 500mV Vce(sat), the phototransistor can sink enough current to drive a logic gate input or a low-power relay coil, but the 20% CTR means the LED drive must be sized to guarantee the output on-state. Turn-on and turn-off times are both 2 µs typical — fast enough for 100 kHz switching, but not for high-speed data isolation.

Obsolete — plan a replacement now

The 4N25 is marked Obsolete by onsemi. For a BOM line that still needs this footprint, the 4N35 is a common drop-in — same 6-DIP pinout, same 5300Vrms isolation, but with a higher minimum CTR (100% at 10 mA). The 4N25 remains ROHS3 compliant. Sourcing is available on an RFQ basis; confirm the quantity and lead time at quote.

Frequently asked questions

Is the onsemi 4N25 obsolete, and what is the replacement?

Yes, the 4N25 is listed as Obsolete. A common pin-compatible replacement is the 4N35, which shares the same 6-DIP footprint and 5300Vrms isolation but offers a higher minimum current transfer ratio (100% at 10 mA vs 20%). Confirm the CTR requirement before swapping.

What is the difference between 4N25 and 4N35?

Both are single-channel optoisolators in 6-DIP with 5300Vrms isolation. The key difference is the minimum CTR: 4N25 is 20% at 10 mA, while the 4N35 is typically 100% at 10 mA. The 4N35 also has a wider operating temperature range (typically -55°C to 100°C, same as 4N25). Pinout is identical.