2N3904

@@ -0,0 +1,47 @@+# 2N3904++**onsemi** · NPN BJT (general purpose) · TO-92++The 2N3904 is the default general-purpose NPN bipolar transistor, in a TO-92 through-hole package. It switches and amplifies small signals up to about 200 mA and 40 V, with a current gain (hFE) of roughly 100 to 300 and a transition frequency near 300 MHz, so it works as a switch, a small-signal amplifier, or a logic-level buffer. The TO-92 leads are E, B, C in order (pin 1 = emitter). Its PNP complement is the 2N3906.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | E | passive | Emitter of the NPN transistor. VEBO breakdown 6.0 V. In TO-92 (viewed from the flat/front, leads down), lead 1 is Emitter. |+| 2 | B | input | Base of the NPN transistor. Controls collector current with hFE typ 100-300 at IC=10 mA, VCE=1.0 V. VBE(sat) ≤ 0.85 V at IC=10 mA, IB=1.0 mA. |+| 3 | C | passive | Collector of the NPN transistor. VCEO breakdown 40 V, VCBO breakdown 60 V, IC continuous max 200 mA. VCE(sat) ≤ 0.2 V at IC=10 mA, IB=1.0 mA. |++## Key specifications++| Parameter | Value |+|---|---|+| Type | NPN bipolar transistor |+| Collector-emitter (VCEO) | 40 V |+| Collector current (IC) | 200 mA |+| DC gain (hFE) | 100-300 |+| Transition freq (fT) | 300 MHz |+| Power dissipation | 625 mW |+| Pinout | E-B-C (pin 1 = emitter) |+| Package | TO-92 |++## Ordering variants++- `2N3904BU (TO-92)`+- `2N3904TA (TO-92, ammo pack)`++## CAD (KiCad official)++- Symbol: `Transistor_BJT:2N3904`+- Footprint: `Package_TO_SOT_THT:TO-92_Inline`+- 3D model: TO-92 (KiCad packages3D)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [onsemi datasheet](https://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/2N3904.pdf) (7 pp, sha256 `39b20929e3d2d854`, retrieved 2026-08-17, tier: manufacturer)+- **Extractor:** `ds2sf` (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.+- **CAD:** KiCad official libraries (CC-BY-SA 4.0).++[Datasheet PDF](docs/2n3904-datasheet.pdf)

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