{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"BD139","brand":"STMicroelectronics","brandSlug":"stmicroelectronics","productSlug":"BD139","canonicalUrl":"https://icboms.com/stmicroelectronics/BD139","factsUrl":"https://icboms.com/api/mcp/products/BD139","rawCanonicalId":null},"summary":{"shortDescription":"STMicroelectronics BD139, NPN general-purpose transistor, 80 V Vceo, 1.5 A Ic, 1.25 W, TO-225AA / TO-126-3 through-hole package, SOT-32-3.","salesMarkdown":"## Medium-power NPN for through-hole designs The BD139 is an NPN epitaxial planar transistor rated for 80 V collector-emitter breakdown and 1.5 A continuous collector current, with a maximum power dissipation of 1.25 W in the TO-126-3 package. It is a general-purpose switching and linear amplifier transistor — common in relay drivers, solenoid drivers, linear regulators, and audio output stages where a through-hole part with a bolt-down tab is preferred over an SMD alternative. The 80 V collector-emitter breakdown voltage means the BD139 can switch or regulate rails up to about 48 V with margin — a 24 V or 48 V industrial supply, a 36 V battery string, or a 12 V automotive rail are all within its safe operating area. The 1.5 A continuous collector current rating supports loads like a medium-sized relay coil (typically 100–300 mA), a small DC motor (500 mA–1 A stall), or the pass element in a 12 V linear regulator delivering up to 1 A. Saturation voltage is 500 mV maximum at 500 mA collector current with 50 mA base drive — a typical switching loss figure for this class of transistor; for lower-loss switching at similar current, look at a Darlington or a MOSFET. ## Thermal budget in a TO-126 tabbed package Maximum junction temperature is 150°C, and the 1.25 W power dissipation is specified with the device in free air — bolting the tab to a heatsink or chassis panel can roughly double the usable dissipation, depending on the thermal interface and airflow. The TO-126-3 package (also known as SOT-32-3) has a metal tab that is electrically connected to the collector — the heatsink must be electrically isolated or the collector rail must be at chassis ground potential. No official successor or second-source is listed on the record.","metaTitle":"BD139 NPN Transistor, 80 V, 1.5 A, TO-126-3","metaDescription":"BD139 NPN transistor: 80 V Vceo, 1.5 A Ic, 1.25 W in TO-126-3 through-hole.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":"ROHS3 Compliant","productStatus":"Obsolete","categoryPath":["Discrete Semiconductors"],"specifications":{"Mfr":"STMicroelectronics","Series":"-","Package":"Tube","Power - Max":"1.25 W","Mounting Type":"Through Hole","Package / Case":"TO-225AA, TO-126-3","Product Status":"Active","Transistor Type":"NPN","lifecycle_stage":"eol_hot","Base Product Number":"BD139","Operating Temperature":"150°C (TJ)","Frequency - Transition":"-","Supplier Device Package":"SOT-32-3","Vce Saturation (Max) @ Ib, Ic":"500mV @ 50mA, 500mA","Current - Collector (Ic) (Max)":"1.5 A","Current - Collector Cutoff (Max)":"100nA (ICBO)","DC Current Gain (hFE) (Min) @ Ic, Vce":"40 @ 150mA, 2V","Voltage - Collector Emitter Breakdown (Max)":"80 V"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$0.6200","priceTiers":[{"qty":1,"price":"$0.66000","currency":"USD"},{"qty":10,"price":"$0.57700","currency":"USD"},{"qty":100,"price":"$0.44250","currency":"USD"},{"qty":500,"price":"$0.34980","currency":"USD"},{"qty":1000,"price":"$0.28875","currency":"USD"}]},"links":{"datasheetUrl":"https://cdn.icboms.com/2b4c847b4457cf87649f8f90311a78a9.pdf","sourceUrl":null,"alternativesUrl":"https://icboms.com/api/mcp/products/BD139/alternatives.json"},"ai":{"faq":[{"question":"Does BD139 come in a surface mount package?","answer":"No — the BD139 is only listed in a through-hole TO-225AA / TO-126-3 package (SOT-32-3). For a surface-mount NPN with similar voltage and current rating, consider the NSS40500UW3T2G or the DXTN07100T-7."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/stmicroelectronics/BD139","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/stmicroelectronics/BD139 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-07-16T16:10:45.214Z","lastPublished":"2026-07-16T16:10:45.214Z","indexable":true}}