MMBT3904LT1 - 40V NPN General Purpose Transistor SOT-23
MPN: MMBT3904LT1 ✓ Hoạt độngMMBT3904LT1 Tóm tắt
An NPN bipolar junction transistor is a three-terminal semiconductor device in which a small base current controls a much larger collector current. Within the broader semiconductor taxonomy, the MMBT3904LT1 sits at: BJT -> bipolar transistor -> discrete semiconductor -> semiconductor. NPN devices conduct when the base is biased above the emitter by approximately 0.7 V, making them the natural choice for low-side switching and for sourcing current to a load tied to a positive rail.
Key features include a 40 V collector-emitter breakdown voltage (VCEO), 60 V collector-base breakdown (VCBO), 6 V emitter-base breakdown (VEBO), 200 mA continuous collector current, 300 MHz transition frequency (fT), DC current gain (hFE) of 100 to 300, and an epitaxial planar die construction. The SOT-23 (TO-236) plastic package supports a 350 mW dissipation rating on a minimum 1 inch² copper pad and operates across a -55 °C to +150 °C junction temperature range.
The part uses an epitaxial planar process that yields a high gain-bandwidth product relative to its small footprint. Its low saturation voltage (VCE(sat a few hundred millivolts at moderate IC) makes it efficient as a saturated switch, while its 300 MHz fT supports general-purpose small-signal RF amplification below the VHF band.
Typical applications include low-side switching of LEDs, relays, and logic-level translators, general-purpose small-signal amplification, inverter and interface circuits, and as a driver for higher-power transistors. The complementary MMBT3906 (PNP) is the natural companion for push-pull and level-shifter topologies.
When designing with this device, observe the 200 mW power dissipation limit: at 200 mA collector current the allowable VCE drops to 1 V before derating begins. A minimum 0.5 inch² of copper pad area is recommended to keep the junction within safe thermal limits in continuous operation.
This page synthesizes distributor pricing, drop-in SOT-23 alternatives, and practical design notes not found on the onsemi datasheet alone, with cross-brand equivalents sourced from verified catalog cross-references.
Bộ thay thế dễ dàng lắp đặt cho MMBT3904LT1 — cùng gói, chân-to-chân tương thích. Các bộ phận yêu cầu hàn PCB bị loại trừ.
Các biến thể trong loạt này
Các mẫu cùng loạt có thể lắp đặt dễ dàng tương thích với MMBT3904LT1 (cùng hình factor và footprint) — khác nhau ở DC Current Gain (hFE), Package, Power Dissipation (PD), Transition Frequency (fT).
MMBT3904LT1G
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
MMBT3904LT3G
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
SMMBT3904LT1G
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
MMBT3904
✅ Drop-InLiên hệ để biết giá
Xem tài liệu →BC847
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
MMBT2222A
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
MMBTA05
✅ Drop-In📋 Tham chiếu thay thế (không có trong danh mục)
MMBT3904LT1 Tỷ lệ tối đa & tính chất điện
| Polarity | NPN |
| N Nap-Emit (Vceo) | 40 V |
| N Nap (Vcbo) | 60 V |
| N Nap-cơ sở (Vebo) | 6 V |
| Continuous Collector Current (IC) | 200 mA |
| Power Dissipation (PD) | 200 mW (on minimum recommended pad) |
| DC Current Gain (hFE) | 100 to 300 |
| Tần số chuyển đổi (ft) | 300 MHz (min) |
| Noise Figure | 5 dB (max) |
| Nhiệt độ mối nối hoạt động | -55 °C to +150 °C |
| Hộp | SOT-23 (TO-236), 3-pin |
| Kiểu lắp đặt | Surface Mount |
| Die Construction | Epitaxial Planar |
| Complementary PNP Part | MMBT3906 |
| Trạng thái RoHS | Compliant (Lead Free version available) |
| AEC-Q101 Qualified | Yes (S-prefix variant) |
Cấu hình chân MMBT3904LT1
| Chân 1 | Emitter — Emitter terminal (grounded for low-side switching) |
| Chân 2 | Base — Base control terminal (current in to turn on) |
| Chân 3 | Collector — Collector terminal (load connection) |
Ứng dụng tiêu biểu
MMBT3904LT1 phù hợp cho 6 Áp dụngs: LED Driver / Low-Side Switch, Logic-Level Translator / Level Shifter, General-Purpose Small-Signal Amplifier, Relay and Solenoid Driver, Inverter and Oscillator Circuits, Sensor Switching and Interface.
LED Driver / Low-Side Switch
The MMBT3904LT1 is widely used as a low-side switch to drive indicator LEDs, optocouplers, and relay coils from 3.3 V or 5 V microcontroller GPIO pins. Its 200 mA collector current comfortably handles single indicator LEDs (10-20 mA) and small signal relays; with hFE of 100-300, a few hundred microamps from the GPIO pin saturates the transistor for clean digital switching. The 40 V VCEO provides substantial headroom above 5 V logic rails, and the SOT-23 footprint saves board space in dense designs. Its 300 ns turn-off time supports PWM dimming above 1 kHz without significant switching loss.
Được đề xuất
Logic-Level Translator / Level Shifter
The MMBT3904LT1 serves as a simple, low-cost logic-level translator between 3.3 V microcontrollers and 5 V peripherals, or between any two rails up to 40 V. Placed in an open-collector configuration with a pull-up resistor on the target rail, it shifts logic levels bidirectionally with no quiescent current beyond the pull-up. The NPN BJT's VBE drop of ~0.7 V and low saturation resistance make it suitable for I2C bus level shifting, GPIO voltage translation, and reset signal buffering. The 200 mA continuous current rating supports driving multiple loads from a single translator stage.
Được đề xuất
General-Purpose Small-Signal Amplifier
The MMBT3904LT1's 300 MHz transition frequency and hFE of 100-300 make it well-suited for general-purpose small-signal AC amplification in audio preamp stages, sensor signal conditioning, and intermediate buffer stages. Its low noise figure (5 dB max) supports microphone preamp and instrumentation front-end designs operating below 100 kHz. The SOT-23 package combined with 200 mW dissipation supports compact analog front-ends on densely populated PCBs where TO-92 packages would be too tall or too large.
Được đề xuất
Relay and Solenoid Driver
For low-power relay and solenoid switching under 200 mA continuous, the MMBT3904LT1 provides a compact driver solution when paired with a flyback diode across the inductive load. Its 40 V VCEO handles typical 12 V and 24 V automotive and industrial relay coils with substantial margin for inductive kick suppression. The high hFE (100-300) means a few milliamps from a logic pin can switch the relay directly, eliminating the need for a Darlington driver in cost-sensitive designs. SOT-23 packaging keeps the BOM compact.
Được đề xuất
Inverter and Oscillator Circuits
The MMBT3904LT1 is a building block for simple astable multivibrators, RC oscillators, and square-wave inverter stages. Its 300 MHz fT supports oscillation frequencies well into the MHz range for crystal-controlled or LC-tank oscillators. Two MMBT3904LT1 transistors plus a complementary MMBT3906 form a classic complementary-pair multivibrator for timing circuits, blinkers, and tone generators. The NPN's 40 V rating also suits use as a line driver in RS-232 / RS-485 interface circuits up to that voltage.
Được đề xuất
Sensor Switching and Interface
The MMBT3904LT1 is widely deployed as a sensor interface switch in industrial controls, automotive ECUs, and consumer electronics. Its low VCE(sat) makes it efficient for switching Hall-effect sensors, reed switches, optocouplers, and thermistor bias networks. In a typical application, it buffers a sensor output to a microcontroller ADC input or digital GPIO, providing isolation and level shifting in one stage. The SMD SOT-23 package supports high-density sensor arrays on compact PCBs.
Được đề xuất
Tóm tắt các sản phẩm được đề xuất
Dữ liệu tham khảo kỹ thuật cho MMBT3904LT1 — so sánh, hướng dẫn thiết kế và thông tin tuân thủ.
Hướng dẫn chọn lựa
So sánh với các sản phẩm thay thế
| Tham số | Sản phẩm này | MMBT3904LT1G | MMBT3904LT3G | SMMBT3904LT1G | MMBT3904 | BC847 | MMBT2222A | MMBTA05 |
|---|---|---|---|---|---|---|---|---|
| Brand | onsemi | onsemi | onsemi | onsemi | onsemi | NXP Semiconductors | onsemi | onsemi |
| Package | SOT-23 | SOT-23 - same | SOT-23 - same | SOT-23 - same | SOT-23 - same | SOT-23 - same | SOT-23 - same | SOT-23 - same |
| Polarity | NPN | NPN | NPN | NPN | NPN | NPN | NPN | NPN |
| VCEO (max) | 40 V | 40 V | 40 V | 40 V | 40 V | 45 V | 40 V | 60 V |
| Continuous Collector Current | 200 mA | 200 mA | 200 mA | 200 mA | 200 mA | 100 mA | 600-800 mA | 500 mA |
| DC Current Gain (hFE) | 100-300 | 100-300 | 100-300 | 100-300 | 100-300 | 110-800 | 40-300 | 50-300 |
| Transition Frequency (fT) | 300 MHz | 300 MHz | 300 MHz | 300 MHz | 300 MHz | 100-300 MHz | 250-300 MHz | 100 MHz |
| Automotive Qualified (AEC-Q101) | No (S-prefix available) | No (S-prefix available) | No (S-prefix available) | Yes | No | No (BC847A qualified variants exist) | No | No |
Bảo phân biệt quan trọng
- Industry-standard SOT-23 NPN with proven second-source ecosystem (vsMMBT2222A)
- Lower collector current rating than BC847 alternative (vsBC847 (NXP))
- Lower VCEO than MMBTA05 alternative (vsMMBTA05)
- AEC-Q101 variant available within the same family (vsBC847)
Ghi chú thiết kế
The MMBT3904LT1 is rated 200 mW continuous dissipation when mounted on a minimum 1 in² copper pad at 25 °C ambient, per the onsemi datasheet MMBT3904LT1/D. Power derates linearly to zero at 150 °C junction. Estimated: at 100 mA IC and 10 V VCE, dissipation is 1 W - well above the 200 mW rating - so duty-cycle limiting or a larger SOT-223/TO-92 package (MPSA18, 2N3904) is required for continuous high-current operation.
Route the base trace as short as possible to minimize stray feedback and switching transients. For switching applications above 10 kHz, place a base resistor (typically 1-10 kΩ) directly at the base pin to dampen input resonance. The SOT-23 thermal pad is the collector lead; do not connect it to high-impedance circuits, and provide at least 0.5 in² copper pour to enhance heat spreading on FR-4.
Do not reverse the emitter and collector - the MMBT3904LT1's forward VCEO is 40 V but reverse VCEO drops to a few volts, and gain in reverse mode is severely degraded. Always include a flyback diode across inductive loads (relays, solenoids) connected between V+ and the collector; the absence of this diode will exceed the 40 V VCEO breakdown on switch-off and destroy the transistor. For logic-level interfacing, ensure VBE(sat) of ~0.7 V is properly overcome by the driving GPIO voltage - 3.3 V logic typically provides adequate margin.
At switching frequencies above 100 kHz, the MMBT3904LT1's transition frequency of 300 MHz provides ~30° of phase margin per stage. For low-distortion small-signal amplifier design, bias the collector at 0.5*VCC and keep the emitter bypass capacitor (typically 10-100 µF) close to the emitter pin to maximize AC gain. The 5 dB noise figure is acceptable for audio applications below 50 kHz but degrades rapidly above the fT/10 corner.
Thông tin tuân thủ
MMBT3904LT1G suffix guarantees RoHS and lead-free. S-prefix SMMBT3904LT1 is AEC-Q101 qualified and PPAP capable for automotive. Standard MMBT3904LT1 is not AEC-Q100 qualified - choose S-prefix variant for automotive designs.
