BC817-40-RF - 45V 0.5A NPN BJT SOT-23 | Taiwan Semiconductor
料号： BC817-40-RF ✓ 量产中| 数量 | 单价 | 小计 |
|---|---|---|
| 1 | $0.09 | $0.09 |
| 10 | $0.07 | $0.70 |
| 100 | $0.05 | $5.00 |
| 500 | $0.04 | $20.00 |
| 1,000 | $0.03 | $30.00 |
| 3,000 | $0.025 | $75.00 |
BC817-40-RF 概述
A bipolar junction transistor (BJT) is a three-terminal semiconductor device consisting of two PN junctions (emitter-base and base-collector) sandwiched in either NPN or PNP polarity. Within the transistor taxonomy, the BC817-40-RF sits in the small-signal BJT category -> general-purpose transistor -> discrete semiconductor. The BJT operates in three regions - active (amplification), saturation (switch on), and cutoff (switch off) - with the base current controlling the much larger collector current through the hFE (DC current gain) ratio. SOT-23 plastic packages enable low-cost, high-volume surface-mount assembly for consumer, industrial, and automotive subsystems.
Key features include a transition frequency (fT) of approximately 100 MHz, a maximum power dissipation of 310 mW, and a continuous collector current rating of 0.5 A (with pulsed capability up to higher levels in some datasheet curves). The device supports both linear amplification and saturated switching topologies and is the NPN complement to the BC807 PNP family. Pin-compatible drop-in alternatives are widely available from multiple manufacturers, simplifying second-sourcing.
Typical applications include LED drivers, relay drivers, signal-level shifters, general-purpose amplifier stages, load switches, DC-DC converter pass elements, and interface buffers between logic and higher-current loads. The high hFE bin (250-600) makes the BC817-40-RF especially suited to high-impedance driver interfaces such as microcontroller GPIO ports driving MOSFET gates or opto-isolator inputs.
When designing with this device, ensure that base drive current is sized for worst-case hFE (250) to guarantee saturation at the minimum specified hFE. Place a base-series resistor to limit base current under fault conditions, and observe 310 mW power dissipation limits in still air without a copper heatsink.
This page synthesizes distributor pricing, multi-vendor drop-in alternatives, and practical design notes that go beyond the manufacturer datasheet, giving the engineer a single decision-ready reference.
直接替换替代料： BC817-40-RF ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
本系列中的变体
可与以下型号直接替换的同系列型号： BC817-40-RF （相同外形与封装尺寸） ——差异在于 Continuous Collector Current (IC), MSL Level, Operating Junction Temperature, Package, RoHS Status.
快速对比工具——选择替代料号进行并排对比：
该产品暂无直接替换替代料。
请求替代料BC817-40-RF 最大额定值与电气特性
| 晶体管类型 | NPN Bipolar Junction Transistor (BJT) |
| 封装 | SOT-23 (TO-236), 3 pins |
| 集电极-发射极电压（Vceo） | 45 V |
| 集电极-基极电压（Vcbo） | 50 V |
| 发射极-基极电压（Vebo） | 5 V |
| Continuous Collector Current (IC) | 0.5 A |
| DC Current Gain (hFE) Bin | 250 to 600 (BC817-40 gain bin) |
| 过渡频率（ft） | 100 MHz |
| Power Dissipation (Pd) | 310 mW |
| 工作结温 | -55 C to +150 C |
| 安装类型 | Surface Mount |
| MSL 等级 | 1 (unlimited) |
| RoHS 状态 | Compliant (per manufacturer product page) |
| Lead-Free | Yes (per Taiwan Semiconductor product page) |
| PNP Complement | BC807 series |
BC817-40-RF 引脚配置
| 引脚 1 | Base (B) — Control input; base current (IB) modulates the collector current via hFE |
| 引脚 2 | Emitter (E) — Common terminal; current exits the transistor through the emitter |
| 引脚 3 | Collector (C) — Main current-carrying terminal; supplies load current |
安全工作区 - BC817-40 (DC, Tamb=25C, mounted on 100 mm^2 1oz Cu)
典型应用
BC817-40-RF 适用于 6 应用s: Microcontroller GPIO LED Driver, Signal-Level Shifter / Logic Level Translator, Relay and Solenoid Driver Switch, MOSFET Gate Driver Interface Stage, General-Purpose Audio Pre-Amplifier Stage, DC-DC Converter Pass Element.
Microcontroller GPIO LED Driver
The BC817-40-RF is ideal for driving indicator LEDs directly from a microcontroller GPIO pin because its 250-600 hFE bin provides very high input sensitivity, allowing a 3.3 V or 5 V GPIO to sink up to tens of milliamps through the transistor with only a few hundred microamps of base drive. With 45 V VCEO and 0.5 A IC, the part also tolerates inductive kickback from relay coils and small solenoids. Place a base resistor (typically 1-10 kOhm) between the GPIO and the base to limit base current under fault conditions; place a flyback diode across any inductive load to protect the collector. The SOT-23 footprint fits directly beneath each LED cluster on a board, simplifying layout.
推荐
Signal-Level Shifter / Logic Level Translator
Use the BC817-40-RF as a one-transistor level shifter between a 3.3 V microcontroller and a 5 V or 12 V peripheral logic input. With 45 V VCEO, the device comfortably handles 12 V logic rails and provides current amplification so a low-current GPIO can drive higher-current loads on the target side. The high hFE bin (250-600) minimizes the input current required to saturate the transistor. A pull-up resistor on the collector side establishes the high-level output voltage, and the base resistor limits base current. This topology is faster and cheaper than dedicated level-shifter ICs for one-off signal lines.
推荐
Relay and Solenoid Driver Switch
The BC817-40-RF functions as a low-side switch for 5 V, 12 V, and 24 V relay coils and small solenoids. The 0.5 A continuous collector current comfortably handles most signal relays; for higher-current contactors, parallel two BC817-40-RF devices or upgrade to a dedicated MOSFET. The 45 V VCEO rating also tolerates the inductive flyback spike if a flyback diode is missed (though the diode is still required for reliability). With 100 MHz fT, switching transients are very fast - place the flyback diode (1N4148 or 1N4007) physically close to the relay coil to minimize radiated EMI.
推荐
MOSFET Gate Driver Interface Stage
The BC817-40-RF serves as a high-gain interface stage between a microcontroller GPIO and the gate of a power MOSFET in low-to-medium frequency switching applications. With hFE 250-600, a 5 V GPIO producing only 5 mA of base drive can sink 1.25-3 A of collector current - more than enough to charge typical logic-level MOSFET gate capacitances in tens of nanoseconds. For very large MOSFETs or high PWM frequencies above 100 kHz, the 100 MHz fT begins to limit switching speed; upgrade to a dedicated MOSFET gate driver IC. The SOT-23 footprint keeps the driver stage compact next to the power MOSFET.
推荐
General-Purpose Audio Pre-Amplifier Stage
Use the BC817-40-RF as a single-transistor common-emitter audio pre-amplifier for low-level signal conditioning, microphone front-ends, and tone-control stages in consumer audio products. With 100 MHz fT, the device provides more than 100x gain-bandwidth product over the 20 Hz-20 kHz audio band. The 250-600 hFE bin allows high input impedance designs with modest base bias currents. For lowest noise, operate at IC around 1 mA where the BC817-40 noise figure is minimized; for highest gain, operate at 10 mA. Pair with the PNP BC807-40 in complementary push-pull output stages.
推荐
DC-DC Converter Pass Element
In low-current linear regulators and small DC-DC converter designs, the BC817-40-RF can serve as the pass element when the load current stays below 0.5 A and the input-output differential is moderate. With 45 V VCEO, the part handles 12 V to 5 V and 24 V to 12 V conversion steps comfortably. For higher-efficiency designs, an LDO or switching regulator is preferred; for low-cost discrete designs, the BC817-40-RF combined with a Zener reference and feedback divider provides a simple three-terminal regulator. The 100 MHz fT is more than sufficient for the loop bandwidth of any linear regulator design.
推荐
推荐产品汇总
工程参考数据： BC817-40-RF ——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 | BC817-40 | BC817-40-7-F | BC817-40-TP | BC817-40 (Diotec) | BC817-40LT1G | BC817-40 (Infineon) |
|---|---|---|---|---|---|---|---|
| Package | SOT-23 (TO-236), 3 pins | SOT-23 (TO-236AB) - same | SOT-23 - same | SOT-23 - same | SOT-23 (TO-236) - same | SOT-23 - same | SOT-23 - same |
| Brand | Taiwan Semiconductor | Nexperia | Diodes Incorporated | Micro Commercial Components | Diotec Semiconductor | onsemi | Infineon Technologies |
| VCEO (max) | 45 V | 45 V | 45 V | 45 V | 45 V | 45 V | 45 V |
| IC (max continuous) | 0.5 A | 0.5 A | 0.5 A | 0.5 A | 0.8 A | 0.5 A | 0.5 A |
| hFE Bin | 250-600 (-40 bin) | 250-600 (-40 bin) | 250-600 (-40 bin) | 250-600 (-40 bin) | 250-600 (-40 bin) | 250-600 (-40 bin) | 250-600 (-40 bin) |
| Power Dissipation Pd | 310 mW | 310 mW | 310 mW | 310 mW | 310 mW | 310 mW | 310 mW |
| Transition Frequency fT | 100 MHz | 100 MHz | 100 MHz | 100 MHz | 100 MHz | 100 MHz | 100 MHz |
| RoHS / Lead-Free | Yes (Taiwan Semiconductor) | Yes (Nexperia) | Yes (Diodes Inc) | Yes (MCC) | Yes (Diotec) | Yes (onsemi) | Yes (Infineon) |
| PNP Complement | BC807-40 | BC807-40 | BC807-40 | BC807-40 | BC807-40 | BC807-40LT1G | BC807-40 |
关键差异点
- Taiwan Semiconductor's BC817-40-RF offers full -40 hFE bin with 250-600 current gain and 100 MHz fT in JEDEC SOT-23 （对比 BC817-40 (Nexperia))
- Highest hFE bin (250-600) of the BC817 series （对比 BC817-25)
- Multi-vendor SOT-23 drop-in availability simplifies second sourcing （对比 Proprietary SOT-23-6 or DFN-packaged transistors)
设计说明
Estimated: at VCE=10V and IC=200mA, power dissipation is 2W. The SOT-23 package has a junction-to-ambient thermal resistance of approximately 430 C/W on a minimum-pad PCB, producing a junction temperature rise of 860 C above ambient - far exceeding the 150 C rating. Either reduce the operating point (stay below approximately 30 mW on a minimum-pad board, or 200 mW with 100 mm^2 1 oz copper heatsink), or upgrade to a DPAK/TO-220 packaged BJT. Always calculate Pd = VCE * IC for the worst-case operating point.
Base-current sizing is the most common BC817-40 design pitfall. Designers sometimes assume the typical hFE (e.g. 400) when sizing the base resistor, then find the transistor will not saturate at worst-case hFE (250) under low temperature. Always size base current for the minimum guaranteed hFE of 250, then add 20-50% margin for aging and temperature effects. For example, to switch 200 mA of collector current, provide at least 200/250 = 0.8 mA of base drive - so a 3.3 V GPIO driving a 3.0 kOhm base resistor gives 1.1 mA, sufficient margin.
When using the BC817-40 as a switch for inductive loads (relays, solenoids, motors), always place a flyback diode (1N4148 for small loads, 1N4007 for larger loads) physically close to the inductor terminals, with the cathode at the positive side. The diode clamps the inductive flyback spike and protects the transistor from exceeding VCEO. Without the diode, even a 5 V relay coil can produce 50-100 V flyback spikes that will avalanche the BC817-40 and eventually cause failure. For switching applications above 100 kHz, add a small RC snubber (10-100 ohm + 1 nF) across the collector-emitter to damp high-frequency ringing.
合规信息
RoHS and lead-free compliance per Taiwan Semiconductor product page at Mouser. Not AEC-Q100 qualified; for automotive-grade equivalents see Nexperia BC817-40-Q or similar -Q suffixed parts. JEDEC TO-236/SOT-23 package outline.
