BC338-25-B1G - NPN BJT 25V 800mA TO-92 | Taiwan Semiconductor
料号： BC338-25-B1G ✓ 量产中| 数量 | 单价 | 小计 |
|---|---|---|
| 1 | $0.07 | $0.07 |
| 10 | $0.06 | $0.60 |
| 100 | $0.048 | $4.80 |
| 500 | $0.038 | $19.00 |
| 1,000 | $0.03 | $30.00 |
BC338-25-B1G 概述
A bipolar junction transistor is a three-terminal current-controlled semiconductor device that amplifies or switches electronic signals. Within the component hierarchy, the BJT belongs to the discrete semiconductor family, sitting below power modules and above integrated driver ICs. NPN BJTs like the BC338-25 conduct when the base is driven positive relative to the emitter, and they remain popular in analog design because of their linear gain characteristics, low cost, and forgiving biasing requirements.
Key features of the BC338-25-B1G include a high collector current rating of 800mA in a compact TO-92 outline, a transition frequency (fT) of 100MHz that comfortably covers audio-frequency driver stages and moderate-speed switching, and a low collector-emitter saturation voltage characteristic of the BC338 family, which reduces conduction losses in switching duty. The device is lead-free and RoHS compliant per the manufacturer's published status.
The BC338 family was originally introduced by European manufacturers such as Siemens and Motorola as NPN silicon AF (audio frequency) transistors emphasizing high current gain, high collector current, and low VCE(sat). Taiwan Semiconductor continues this established industry-standard part as a second-source, so designers can adopt it without redesigning legacy BC338 sockets or layouts.
Typical applications include audio driver stages and low-power output stages, relay and LED drive circuits, low-side switching of loads up to 800mA, signal amplification in consumer and industrial equipment, and general-purpose linear amplifiers where a TO-92 through-hole package is preferred for hand assembly or prototyping.
One design consideration: the BC338-25 is specified at 25V VCEO, lower than the 50V rating of its sibling BC337-25. Verify that your supply transients, especially inductive load kickback from relays or solenoids, stay below the 25V limit, or use a flyback clamp diode.
This page synthesizes distributor pricing context, drop-in alternatives, pinout data, and practical design notes not consolidated in the manufacturer datasheet.
直接替换替代料： BC338-25-B1G ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
快速对比工具——选择替代料号进行并排对比：
BC338-16-B1G
✅ 直接替换 ⚠️ 规格未核验📋 参考替代料（不在目录中）
BC338-40-B1G
✅ 直接替换 ⚠️ 规格未核验📋 参考替代料（不在目录中）
BC338-25
✅ 直接替换📋 参考替代料（不在目录中）
BC338-25
✅ 直接替换📋 参考替代料（不在目录中）
BC337-25
✅ 直接替换📋 参考替代料（不在目录中）
BC337-25
✅ 直接替换📋 参考替代料（不在目录中）
BC338-25-B1G 最大额定值与电气特性
| 晶体管类型 | NPN Bipolar Junction Transistor (BJT) |
| 集电极-发射极电压（Vceo） | 25 V |
| Collector Current (IC, continuous) | 800 mA |
| DC Current Gain (hFE, -25 grade) | 160 to 400 |
| 过渡频率（ft） | 100 MHz |
| Power Dissipation (PT) | 625 mW |
| 封装 | TO-92 (through hole) |
| 安装类型 | Through Hole |
| Pin Configuration | 1-Collector, 2-Base, 3-Emitter |
| Polarity | NPN |
| Configuration | Single transistor |
| Gain Grade | -25 (hFE 160-400) |
| RoHS 状态 | Lead free / RoHS Compliant |
| Typical Applications | AF amplifier and switching applications |
BC338-25-B1G 引脚配置
| 引脚 1 | Collector — Collector terminal - connects to the load/high-potential side |
| 引脚 2 | Base — Base terminal - control input, driven through a current-limiting resistor |
| 引脚 3 | Emitter — Emitter terminal - typically connected to ground in low-side NPN configurations |
典型应用
BC338-25-B1G 适用于 6 应用s: Audio Frequency Driver Stages, Relay and Solenoid Low-Side Switching, LED Drive and Indicator Circuits, Small-Signal and Preamplifier Circuits, Industrial and Consumer Board-Level Switching, Repair, Retrofit, and Legacy Equipment Maintenance.
Audio Frequency Driver Stages
The BC338-25-B1G was originally specified by Siemens and Motorola as an NPN silicon AF (audio frequency) transistor, and that heritage carries into the Taiwan Semiconductor version. Its hFE of 160-400 provides ample current gain for class-AB driver stages, while the 100MHz transition frequency ensures flat response and negligible phase shift across the entire audio band, where the fT is three orders of magnitude above 20kHz. In a typical driver role the transistor sits between a small-signal voltage-amplifier stage and a power output pair, delivering tens to hundreds of milliamps of base drive with low distortion. The low VCE(sat) characteristic of the BC338 family reduces heating in bias networks. Because the part is a commodity TO-92 through-hole device, it is also ideal for point-to-point wiring in hobby amplifiers and professional audio service repair, where legacy BC338 sockets accept it directly without lead re-forming.
推荐
Relay and Solenoid Low-Side Switching
The BC338-25-B1G drives small relays and solenoids from microcontroller GPIO pins, exploiting its 800mA collector current rating, which comfortably covers common 5V and 12V relays drawing 30-70mA coil current. Configured as a low-side switch with the emitter grounded, the base is fed through a 1k-4.7k ohm resistor from the logic pin; the hFE of 160-400 guarantees hard saturation at these coil currents. A flyback clamp diode across the coil is mandatory because inductive kickback can transiently exceed the 25V VCEO rating - add a 1N4148 or 1N4007 across the coil to protect the transistor. The low VCE(sat) of the BC338 family keeps on-state dissipation to a few milliwatts, so the TO-92 package stays cool even in sealed enclosures. This is a staple circuit in home automation, appliance control, and industrial interlock boards where through-hole assembly is still used.
推荐
LED Drive and Indicator Circuits
The BC338-25-B1G switches high-current LED strings and indicator lamps that exceed the 20mA sink capability of typical microcontroller outputs. With 800mA collector current capacity, a single BC338-25 can drive multiple parallel LED branches or high-brightness LEDs at 100-350mA, with the series resistor setting the current and the base resistor sized for roughly 1/10 of collector current to ensure saturation. The 100MHz fT is far beyond any PWM frequency used for LED dimming, so the transistor adds no visible switching delay even at 100kHz PWM dimming rates used to avoid perceptible flicker. In through-hole designs the TO-92 package simplifies hand assembly and thermal spreading. The main design check is power: estimated dissipation equals VCE(sat) x IC plus base-drive loss, which for 200mA at 0.3V VCE(sat) is only about 60mW, leaving a wide margin to the 625mW package limit.
推荐
Small-Signal and Preamplifier Circuits
As a general-purpose NPN amplifier, the BC338-25-B1G serves in microphone preamps, sensor buffer stages, and discrete op-amp input pairs. The -25 gain bin (hFE 160-400) balances input impedance and noise: higher hFE reduces the base current drawn from high-impedance sources, improving voltage gain in common-emitter stages where Av is approximately -gm x RC. The 100MHz transition frequency means the beta cutoff frequency (fT/hFE, roughly 250kHz-600kHz) sits comfortably above audio, so gain stays flat where it matters. Designers bias the device with a resistor divider on the base and an emitter degeneration resistor to stabilize the operating point against hFE spread; using the -25 grade rather than ungraded stock tightens production consistency. For legacy equipment repair, this Taiwan Semiconductor part directly replaces Siemens, Motorola, and Philips BC338-25 devices in existing sockets with identical collector-base-emitter lead order.
推荐
Industrial and Consumer Board-Level Switching
On industrial control boards and consumer appliance PCBs, the BC338-25-B1G acts as a level-shifting and load-switching workhorse: driving optocoupler LEDs, biasing MOSFET gates, pulling status lines, and switching small motors or buzzers. The through-hole TO-92 package offers superior mechanical robustness for wave-soldered and hand-soldered production, and its worldwide second-source availability from Taiwan Semiconductor, Diotec, and onsemi protects against allocation. The 25V rating suits 5V, 12V, and 24V-rail edge applications - for a 24V rail, verify that inductive transients are clamped below 25V or specify the 50V BC337-25 instead. The 625mW dissipation limit and standard hFE grading make thermal and drive calculations straightforward for volume production. Because the part is RoHS compliant and lead free, it fits directly into current environmental-compliance manufacturing flows without process exceptions.
推荐
Repair, Retrofit, and Legacy Equipment Maintenance
The BC338 family has been manufactured since the 1970s by Siemens, Motorola, Philips, and Fairchild, so BC338-25 devices appear throughout legacy test equipment, audio gear, telecommunications hardware, and industrial controllers. The Taiwan Semiconductor BC338-25-B1G is the modern RoHS-compliant continuation of this footprint, making it a primary service stock item for maintenance depots. The collector-base-emitter TO-92 pin order is identical across all family vendors and across BC337/BC338 siblings, so a technician can substitute the BC338-25-B1G for a failed original without consulting vendor-specific pinouts. Where the original circuit runs above 20V or drives inductive loads, the BC337-25 (50V, same pinout) is the safer service substitute per published cross-reference data. Typical replacement scenarios include audio amplifier driver transistors, relay drivers in vintage control units, and gain stages in instrument front ends where original Motorola or Siemens stock is exhausted.
推荐
推荐产品汇总
工程参考数据： BC338-25-B1G ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | BC338-16-B1G | BC338-25 (Diotec) | BC338-25 (onsemi) | BC337-25 |
|---|---|---|---|---|---|
| Package | TO-92 (through hole) | TO-92 - same | TO-92 - same | TO-92 - same | TO-92 - same |
| Brand | Taiwan Semiconductor | Taiwan Semiconductor | Diotec Semiconductor | onsemi | onsemi / Fairchild |
| VCEO (Collector-Emitter Voltage) | 25 V | 25 V | 25 V | 25 V | 50 V |
| Collector Current | 800 mA | 800 mA | 800 mA | 800 mA | 800 mA |
| hFE Range (gain grade) | 160 to 400 (-25) | 100 to 250 (-16) | 160 to 400 (-25) | 160 to 400 (-25) | 160 to 400 (-25) |
| Power Dissipation | 625 mW | 625 mW | 625 mW | 625 mW | 625 mW |
| Pin Configuration | 1-Collector, 2-Base, 3-Emitter | C-B-E - same | C-B-E - same | C-B-E - same | C-B-E - same |
关键差异点
- Identical parametric spec with dual sourcing security （对比 BC338-25 (Diotec Semiconductor))
- Lower cost at equal gain class （对比 BC337-25 (onsemi))
- Gain-grade flexibility within the same footprint （对比 BC338-40-B1G)
设计说明
The single most common failure mode for the BC338-25-B1G is inductive kickback exceeding the 25V VCEO rating. When switching relays, solenoids, or small motors, the collapsing magnetic field can drive the collector tens of volts above the supply rail for microseconds, avalanching and degrading the junction. Always place a flyback diode (1N4148 for fast coils, 1N4007 for relays) directly across the load. If the supply rail itself is above 20V, specify the pin-compatible BC337-25 (50V) instead of adding clamp circuitry.
For switching applications, size the base drive for approximately IC/10 (for example 30mA base current for a 300mA load) rather than relying on the 160-400 small-signal hFE figure, which falls sharply at high collector current. Estimated dissipation in saturation: VCE(sat) x IC; at 500mA and an estimated VCE(sat) of 0.3V this is only 150mW, well within the 625mW TO-92 limit. In linear (Class-A) duty, however, dissipation is (VCE x IC) and can approach the limit - verify junction temperature at maximum ambient.
The TO-92 package dissipates heat primarily through its leads, so keep collector and emitter leads at least 10mm long or connect to generous copper pad area when operating above 300mW estimated dissipation. In hand-assembled and prototyping boards, the flat-face marking shows the pin order clearly: with the flat face toward you and leads down, pins run collector-base-emitter left to right. Place base resistors close to the base lead to minimize pickup in high-gain amplifier layouts.
合规信息
RoHS status Lead free / RoHS Compliant per Taiwan Semiconductor product data (abc-semi distributor listing). REACH, halogen-free, and conflict-minerals status not stated in provided data.
