Gate drive optoisolator for industrial power stages
The FOD3125 is a single-channel gate drive optoisolator from onsemi's OPTOPLANAR® series, designed to drive IGBTs and MOSFETs in motor drives, UPS systems, and industrial power supplies. It provides 5000Vrms of galvanic isolation between the controller and the power stage, with a peak output current of 3A to handle gate charge delivery at switching frequencies up to several hundred kilohertz.
Parametric strengths for switching applications
The 3A peak output current and 2A source/sink capability allow the FOD3125 to drive medium-power IGBTs and MOSFETs directly, reducing the need for a separate buffer stage. Common-mode transient immunity of 35kV/µs minimum is the standout spec for motor drive environments: it prevents the output from false-triggering when the power stage switches at high dv/dt, which is a common failure mode in cheaper optocouplers. The input side requires a forward voltage of 1.5V typical with a maximum DC forward current of 25 mA, compatible with standard 3.3V or 5V logic outputs through a current-limiting resistor.
It is ROHS3 compliant and UL approved. The through-hole 8-DIP package is widely stocked across distribution channels; lead times are typically manageable for a mature optoisolator line. For BOM planning, the part is single-sourced to onsemi, but the OPTOPLANAR® series has been stable for years with no PCN activity.
Package and design-in notes
The 8-DIP package (0.300-inch row spacing, 7.62mm body width) is a through-hole format that suits both prototyping and production. The 8-PDIP supplier device package has a standard 2.54mm pin pitch, which simplifies manual assembly and rework. No exposed thermal pad — the part relies on the DIP body's natural convection for heat dissipation, so derate the output current if ambient exceeds 85°C.