BC338 - NPN 800mA, 20V VCEO Transistor TO-92 | Motorola
部品番号: BC338 ✗ 生産終了| 数量 | 単価 | 小計 |
|---|---|---|
| 1 | $0.12 | $0.12 |
| 10 | $0.1 | $1.00 |
| 100 | $0.07 | $7.00 |
| 500 | $0.05 | $25.00 |
| 1,000 | $0.04 | $40.00 |
BC338 概要
A bipolar junction transistor is a current-controlled semiconductor device used for amplification and switching. Within the component hierarchy, the BC338 belongs to the small-signal transistor family: NPN transistor -> BJT -> discrete semiconductor. NPN devices conduct when the base is driven positive relative to the emitter, making them the default choice for low-side switching and class-A/AF amplifier stages.
Key features documented across manufacturer datasheets (Motorola, Siemens) include high current gain, high collector current capability, and low collector-emitter saturation voltage. The family is subdivided into hFE gain groups -16, -25, and -40, allowing designers to select a gain window matched to biasing requirements. The device is especially suited for AF-driver stages and low-power output stages.
The BC338 uses NPN silicon epitaxial planar construction. Its 625 mW dissipation rating (measured on an FR-4 test board per the Mouser-hosted datasheet) supports low-power output stages, while the 800 mA collector current rating is unusually high for a TO-92 small-signal part, distinguishing it from lower-current peers like the BC547/BC548 family (100 mA class). Maximum VCB is 30 V and VEB is 5 V.
Typical applications include audio frequency driver stages, low-power output stages, relay and LED low-side switching from microcontroller GPIO, and general-purpose amplification in consumer electronics.
Design consideration: verify the pinout of any substitute before insertion - common equivalents such as 2N2222 use a different lead order (E-B-C versus the BC338 C-B-E arrangement).
This page synthesizes datasheet ratings, cross-reference equivalents, and drop-in replacement guidance not consolidated in any single manufacturer datasheet.
ドロップイン代替品: BC338 — 同一パッケージでピン互換。PCBの作り直しが必要な異なるパッケージの部品は除外されています。
クイック比較ツール — 並列比較する代替部品を選択:
BC338-16
✅ ドロップイン📋 参考代替品（カタログ未掲載）
BC338-25
✅ ドロップイン📋 参考代替品（カタログ未掲載）
BC338-40
✅ ドロップイン📋 参考代替品（カタログ未掲載）
BC338CP
✅ ドロップイン📋 参考代替品（カタログ未掲載）
BC337
✅ ドロップイン📋 参考代替品（カタログ未掲載）
BC338 最大定格＆電気的特性
| トランジスタタイプ | NPN Bipolar Junction Transistor (BJT) |
| Technology | Silicon Epitaxial Planar |
| Maximum Collector Current (Ic) | 0.8 A |
| Maximum Collector-Base Voltage (Vcb) | 30 V |
| Maximum Collector-Emitter Voltage (Vceo) | 20 V |
| Maximum Emitter-Base Voltage (Veb) | 5 V |
| Maximum Collector Power Dissipation (Pc) | 0.625 W |
| hFE Gain Groups | -16, -25, -40 |
| Saturation Voltage | Low VCE(sat) (per Siemens datasheet) |
| Primary Use | AF-driver stages and low power output stages |
| パッケージ | TO-92 (plastic) |
| Pinout | C-B-E (flat side facing you, leads down) |
| 実装タイプ | Through Hole |
| Polarity | NPN |
| Complementary PNP | BC328 / SBC328 family |
BC338 ピン構成
| ピン 1 | Collector — Collector terminal (leftmost lead, flat side facing viewer, leads down) |
| ピン 2 | Base — Base control terminal (center lead) |
| ピン 3 | Emitter — Emitter terminal (rightmost lead) |
主な用途
BC338 の用途: 6 件s: Audio Frequency Driver Stages, Low-Power Output Stages, Microcontroller GPIO Low-Side Switching, General-Purpose Amplification, LED Driver and Indicator Circuits, Relay and Solenoid Actuation.
Audio Frequency Driver Stages
The BC338 was purpose-designed for AF-driver stages, per the Motorola and Siemens datasheets. Its high DC current gain and low collector-emitter saturation voltage let it drive the output pair of a class-AB audio amplifier with minimal drive power, while the 800 mA collector rating accommodates the signal swings of low-power output stages. In a typical driver position, the transistor operates in class-A with the gain group (-16/-25/-40) chosen to match the bias network. Unlike general-purpose small-signal parts limited to 100-200 mA, the BC338 sustains the peak currents of output-stage drive without current starvation, improving dynamic headroom. The trade-off versus a dedicated audio transistor is a modest fT and higher noise floor, so it suits consumer and hobby audio rather than low-noise preamplifier front ends.
おすすめ
Low-Power Output Stages
With 800 mA maximum collector current and 625 mW dissipation, the BC338 serves as the output device in low-power audio and driver output stages where a TO-92 package suffices. The low VCE(sat) documented in the Siemens datasheet minimizes conduction loss, keeping junction temperature manageable at the 625 mW limit on a standard FR-4 board (76 mm x 114 mm x 1.57 mm per test conditions). Gain-group grading (-16/-25/-40) enables matched output pairs for reduced crossover distortion. Compared with larger TO-126/TO-220 output transistors, the BC338 saves board area and cost but caps output power at roughly the few-hundred-milliwatt class; above that, step up to a packaged power device with proper heatsinking.
おすすめ
Microcontroller GPIO Low-Side Switching
The BC338 is a robust low-side switch for driving relays, LEDs, and small loads directly from 3.3 V or 5 V microcontroller GPIO pins. The 800 mA rating covers most relay coils and LED strings, and the high hFE groups allow generous base-resistor values - for example, a 1 kohm base resistor from 5 V GPIO delivers roughly 4 mA of base drive, which at a guaranteed gain of 100 supports hundreds of milliamps of collector current with low saturation voltage. Compared with a 2N2222, the BC338's higher current ceiling provides margin for inrush, but remember the pinout differs (C-B-E versus E-B-C), so PCB footprints must be re-verified when substituting. Always add a flyback diode across inductive loads.
おすすめ
General-Purpose Amplification
As an NPN epitaxial planar transistor, the BC338 performs general-purpose small-signal amplification - common-emitter and emitter-follower stages in consumer equipment, sensor conditioning, and level shifting. Its high current gain groups give designers predictable bias points, and the 20 V VCEO covers 12 V and 15 V rails with margin. The 5 V VEB limit requires care in reverse-biased input conditions; a series base resistor or protection diode guards against emitter-base breakdown in level-shift service. Against the BC547/BC548 class (100 mA), the BC338 trades slightly higher capacitance for 8x the collector current, making it preferable where the stage also drives a load rather than only feeding a high-impedance next stage.
おすすめ
LED Driver and Indicator Circuits
The BC338 drives high-current LED strings and indicator lamps that exceed the capability of 100 mA-class transistors. Its 800 mA rating supports high-brightness LEDs and short LED chains from a 5 V or 12 V supply, while low VCE(sat) keeps wasted power and heat low in the on-state. A typical circuit uses a GPIO through a 1-2.2 kohm base resistor with the LED string and current-limiting resistor in the collector path; dissipation stays well under the 625 mW ceiling when the ballast resistor absorbs the headroom. Compared with a dedicated constant-current LED driver IC, the BC338 solution is cheaper and simpler but lacks current regulation, so the ballast resistor must be sized for LED forward-voltage tolerance.
おすすめ
Relay and Solenoid Actuation
For switching 5 V and 12 V relays and small solenoids, the BC338 offers higher coil-current headroom than typical small-signal BJTs. The 800 mA maximum covers most signal relays and small telecom relays; the high hFE groups ensure full saturation from modest base drive, keeping VCE(sat) - and thus on-state heating - low. Design practice: size the base resistor for forced beta of roughly 10-20 to guarantee saturation at the coil's inrush current, place a 1N4148 or Schottky flyback diode across the coil to clamp the inductive kick below the 20 V VCEO rating, and verify continuous coil current against the 625 mW package dissipation. Against a logic-level MOSFET, the BJT solution avoids gate-drive concerns at 3.3 V at the cost of base-drive current.
おすすめ
おすすめ製品の概要
エンジニアリング参考データ: BC338 — 比較、設計ガイダンス、コンプライアンス情報。
選定ガイド
代替品との比較
| パラメータ | この製品 | BC338-16 | BC338-25 | BC338-40 | BC338CP | BC337 |
|---|---|---|---|---|---|---|
| Package | TO-92 | TO-92 - same | TO-92 - same | TO-92 - same | TO-92 - same | TO-92 - same |
| Brand | Motorola (legacy; onsemi lineage) | onsemi (Motorola lineage) | onsemi (Motorola lineage) | onsemi (Motorola lineage) | onsemi (Motorola lineage) | onsemi |
| Polarity | NPN | NPN | NPN | NPN | NPN | NPN |
| Pinout | C-B-E | C-B-E | C-B-E | C-B-E | C-B-E | C-B-E |
主な差別化要因
- 800 mA collector current in a TO-92 small-signal package （vs BC337)
- Gain-group grading for reproducible biasing （vs BC338-16)
- Higher voltage headroom option via BC337 （vs BC337)
設計ノート
Pin order is the number-one substitution trap with the BC338. The BC338 uses a C-B-E lead order (flat side facing viewer, leads down), while popular equivalents such as the 2N2222, 2N4401, and S8050 use different lead arrangements. The vector4engineering equivalent list explicitly warns that the pin configuration of listed equivalents may differ from the BC338. Always physically verify lead order with a multimeter diode test (two junctions to the base) before soldering a substitute into a BC338 footprint.
Estimated: the 625 mW dissipation rating assumes specific test conditions - the Mouser-hosted BC337/BC338 datasheet cites an FR-4 board of 76 mm x 114 mm x 1.57 mm. Driving the part near the limit at high ambient temperature risks exceeding maximum junction temperature. As a rule of thumb, derate power linearly above 25 C ambient, and keep continuous dissipation below roughly half the rated maximum (about 300 mW) in enclosed enclosures to preserve long-term reliability.
Respect the 5 V emitter-base breakdown limit. In switching circuits with inductive loads (relays, solenoids), the flyback transient can appear across the emitter-base junction through the base network and cause avalanche degradation of hFE. Fit a flyback diode across every inductive load and keep the base drive impedance low enough that clamp current flows through the diode rather than the base-emitter junction. For level-shifter duty where the base may be reverse-biased, add a series base resistor or a small-signal clamp diode.
コンプライアンス情報
Original Motorola BC338 predates modern RoHS/REACH declarations; compliance status for this legacy part is not stated in the provided datasheet sources.
