{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"FODM121","brand":"onsemi","brandSlug":"onsemi","productSlug":"FODM121","canonicalUrl":"https://icboms.com/onsemi/FODM121","factsUrl":"https://icboms.com/api/mcp/products/FODM121","rawCanonicalId":null},"summary":{"shortDescription":"onsemi FODM121 transistor output optocoupler, 1-channel, DC input, 3750Vrms isolation, 50-600% CTR at 5mA, 80V output, 80mA output current, 4-SMD Gull Wing package, Tube.","salesMarkdown":"## Galvanic isolation for signal transfer in industrial control The onsemi FODM121 is a single-channel transistor-output optocoupler that provides 3750Vrms galvanic isolation between a DC input LED and an output phototransistor. This isolation rating is sufficient for basic insulation in mains-connected industrial control circuits, PLC digital inputs, and motor drive feedback paths where ground loops or voltage transients must be blocked. At the 50% floor, a 5mA input still guarantees 2.5mA of output drive, enough to saturate a downstream logic gate or relay coil interface. ## Output ratings and switching speed for BOM planning The output transistor is rated for 80V collector-emitter voltage and 80mA continuous output current, with a Vce saturation of 400mV max. The 80mA ceiling means it is not suited for driving solenoids or incandescent lamps without a buffer transistor. Rise and fall times are 3µs typical each, setting a practical switching ceiling around 100 kHz for digital signals. For 50/60 Hz mains zero-cross detection or low-speed serial data, this is more than adequate; for high-speed fieldbus isolation it falls short — the propagation delay asymmetry would skew the bit timing. The forward LED requires 1.3V max at up to 50mA continuous. The 50mA absolute maximum forward current means the series resistor must be sized to keep the LED within its safe operating area across the full input voltage range, especially if the input rail exceeds 5V. ## Active lifecycle and compliance documentation The surface-mount 4-SMD Gull Wing package (supplier device package 4-SMD) is compatible with standard reflow soldering profiles. The tube packaging is typical for prototype and low-volume assembly; for high-volume pick-and-place, verify with your distributor whether tape-and-reel options are available on alternate order codes within the same family.","metaTitle":"onsemi FODM121 Optoisolator, 3750Vrms, 50-600% CTR, 4-SMD","metaDescription":"onsemi FODM121 transistor output optocoupler, 3750Vrms isolation, 50-600% CTR range at 5mA. Active production, ROHS3 compliant.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":"ROHS3 Compliant","productStatus":"Active","categoryPath":["Optoisolators"],"specifications":{"Package":"Tube","Input Type":"DC","Output Type":"Transistor","Mounting Type":"Surface Mount","Package / Case":"4-SMD, Gull Wing","lifecycle_stage":"eol_hot","Number of Channels":"1","Voltage - Isolation":"3750Vrms","Vce Saturation (Max)":"400mV","Operating Temperature":"-40°C ~ 110°C","Rise / Fall Time (Typ)":"3µs, 3µs","Voltage - Output (Max)":"80V","Supplier Device Package":"4-SMD","Current - Output / Channel":"80mA","Current Transfer Ratio (Max)":"600% @ 5mA","Current Transfer Ratio (Min)":"50% @ 5mA","Voltage - Forward (Vf) (Typ)":"1.3V (Max)","Current - DC Forward (If) (Max)":"50 mA"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$0.66","stockQuantity":0,"priceTiers":[{"qty":1,"price":"$0.66000","currency":"USD"},{"qty":10,"price":"$0.43600","currency":"USD"},{"qty":100,"price":"$0.28840","currency":"USD"},{"qty":1000,"price":"$0.22265","currency":"USD"},{"qty":2000,"price":"$0.20119","currency":"USD"},{"qty":5000,"price":"$0.18778","currency":"USD"},{"qty":10000,"price":"$0.18107","currency":"USD"},{"qty":25000,"price":"$0.17839","currency":"USD"}]},"links":{"datasheetUrl":"https://cdn.icboms.com/269c736c440b53ce097423b4caa3ac66.pdf","sourceUrl":null},"ai":{"faq":[{"question":"What is the closest functional second-source to FODM121 — can FODM1009 drop in?","answer":"The FODM1009 is a close peer with DC input, transistor output, single channel, and surface-mount package. However, FODM1009 offers 5000Vrms isolation versus 3750Vrms on the FODM121, and its rise/fall times are 5.7µs/8.5µs versus 3µs/3µs. The Vce saturation is lower at 300mV versus 400mV. These differences mean a direct drop-in replacement without reviewing the circuit's isolation margin and switching speed requirements is not guaranteed. Verify the application's isolation voltage and timing budget before substituting."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/onsemi/FODM121","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/onsemi/FODM121 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-07-22T19:45:10.375Z","lastPublished":"2026-07-22T19:45:10.375Z","indexable":true}}