{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"BC817-40","brand":"STMicroelectronics","brandSlug":"stmicroelectronics","productSlug":"BC817-40","canonicalUrl":"https://icboms.com/stmicroelectronics/BC817-40","factsUrl":"https://icboms.com/api/mcp/products/BC817-40","rawCanonicalId":null},"summary":{"shortDescription":"BC817-40 NPN transistor, 45 V VCEO, 500 mA Ic, 250 mW, hFE 250 min at 100 mA, 100 MHz, SOT-23-3, surface mount.","salesMarkdown":"It is part of the BC817 family, distinguished by its -40 hFE grade — a minimum DC current gain of 250 at 100 mA collector current and 1 V VCE. This gain band makes it a common choice for general-purpose switching and linear amplification in low-power circuits, such as relay drivers, LED drivers, and signal preamplifiers on compact PCBs. ## The -40 suffix: why the hFE grade matters The BC817 family offers two hFE grades: the -25 (minimum gain 160 at 100 mA) and the -40 (minimum gain 250 at 100 mA). The -40 grade provides higher guaranteed gain, which is useful when the base drive is limited — for example, when driving the transistor directly from a microcontroller GPIO without a separate driver stage. If your design relies on a tight gain window, verify that the -40's 250 minimum meets your saturation margin; the -25 variant may not hold up under the same base current. ## Obsolete status and sourcing reality The BC817-40 is supplied in a SOT-23-3 package (also referred to as TO-236-3 or SC-59). It is a surface-mount device — not through-hole — so it suits automated assembly and compact layouts. The SOT-23-3 footprint is widely used across small-signal transistors, which simplifies board-level replacement if a pin-compatible substitute is sourced.","metaTitle":"BC817-40 NPN Transistor, 45 V, 500 mA, SOT-23-3, Obsolete","metaDescription":"BC817-40 NPN transistor: 45 V VCEO, 500 mA Ic, hFE 250 min at 100 mA. SOT-23-3 surface mount.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Obsolete","categoryPath":["Discrete Semiconductors"],"specifications":{"Mfr":"STMicroelectronics","Series":"-","Package":"Tape & Reel (TR); Cut Tape (CT)","Power - Max":"250 mW","Mounting Type":"Surface Mount","Package / Case":"TO-236-3, SC-59, SOT-23-3","Product Status":"Obsolete","Transistor Type":"NPN","lifecycle_stage":"eol_hot","Base Product Number":"BC817","Operating Temperature":"150°C(TJ)","Frequency - Transition":"100MHz","Supplier Device Package":"SOT-23-3","Vce Saturation (Max) @ Ib, Ic":"700mV @ 50mA, 500mA","Current - Collector (Ic) (Max)":"500 mA","Current - Collector Cutoff (Max)":"100nA (ICBO)","DC Current Gain (hFE) (Min) @ Ic, Vce":"250 @ 100mA, 1V","Voltage - Collector Emitter Breakdown (Max)":"45 V"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$0.3600","priceTiers":null},"links":{"datasheetUrl":"https://cdn.icboms.com/f7ea92b8b149265eb99d0f7f8e15ba35.pdf","sourceUrl":null,"alternativesUrl":"https://icboms.com/api/mcp/products/BC817-40/alternatives.json"},"ai":{"faq":[{"question":"What is the replacement for BC817-40?","answer":"The manufacturer has not published an official successor for the BC817-40. For a pin-compatible alternative, look for another NPN transistor in SOT-23-3 with a 45 V VCEO, 500 mA Ic rating, and a minimum hFE of 250 at 100 mA — many general-purpose small-signal transistors from other vendors meet these parameters. Verify the gain band and saturation voltage against your circuit before substituting."},{"question":"What is the difference between BC817-25 and BC817-40?","answer":"The difference is the hFE gain grade. The BC817-25 has a minimum DC current gain of 160 at 100 mA, while the BC817-40 has a minimum of 250 at the same test condition. Both share the same 45 V VCEO, 500 mA Ic, and SOT-23-3 package — the choice depends on whether your base drive can tolerate the lower gain of the -25 grade."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://icboms.com/stmicroelectronics/BC817-40","citationPolicyUrl":"https://icboms.com/llms.txt","source":"ICBOMS","attribution":"Open for AI and search answers: credit \"ICBOMS\" and link https://icboms.com/stmicroelectronics/BC817-40 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-07-16T14:28:40.964Z","lastPublished":"2026-07-16T14:28:40.964Z","indexable":true}}