The MMBT3904 is a general-purpose SMD transistor, which comes in an SOT-23 Package. This transistor has general marking codes of 1 AM, K1N, 7A%, and s1A based on different manufacturers. In most cases, you can see 1 AM as the marking code. In this article, we share the information about its Pinout, Specifications, and Equivalent transistors for replacement.
What is MMBT3904 SMD Transistor?
MMBT3904 is an NPN transistor that comes in SOT-23 surface mount packaging. This is a general-purpose BJT transistor. It is mainly used for general-purpose signal amplification and switching circuits. This SMD transistor has the collector-emitter voltage of 40V and collector current of 200mA. It is enough to operate on medium voltage circuits.
Different Marking Codes Based on Manufacturer
| Manufacturer | Marking Code |
|---|---|
| Standard / Generic | 1AM |
| Diodes Inc. | K1N |
| Nexperia | 7B% |
| Infeneon | s1A |
MMBT3904 Transistor Pinout
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1AM SMD Transistor (MMBT3904)
✔ NPN Transistor
✔ Approx. 40V Collector Voltage
✔ Approx. 200mA Current
✔ SOT-23 Package
Specifications may vary by seller
To check the pinout of this SMD transistor, you just hold the transistor’s labelling on top and place it on a flat surface. From the top view 1 pin is on one side, and two pins are on the opposite side. The pinout will be counted from 2 pins side of left to right and top. pin 1, pin 2, and pin 3. It is a base emitter and collector.
Pinout Configuration
| Pin Number | Pin Name |
|---|---|
| 1 | Base (B) |
| 2 | Emitter (E) |
| 3 | Collector (C) |
Specifications
- Type: NPN Silicon Epitaxial Planar Transistor
- Package: SOT-23 (Surface Mount)
- Collector-Emitter Voltage is 40V
- Collector Current is 200mA
- Power Dissipation is Approximately 300mW to 350mW
- DC Current Gain is 100 to 300
- Transition Frequency is >300MHz
Equivalent Transistors for Replacement
MMBT3904LT1G, MMBT4401, MMBTA06, MMBTA05, FMMT2222A are the direct replacement options and BC847, S8050, BSR17A are common alternatives. you must check the pinout and specifications before replacing the transistors.
MMBT3904 vs MMBT2222A Comparison
This is a simple comparison between the common SMD transistor of MMBT2222A with MMBT3904 and which are given below,
| Feature | MMBT3904 | MMBT2222A |
|---|---|---|
| Max Collector Current (Ic) | ~200 mA | ~600 to 800 mA |
| Collector-Emitter Voltage (Vce) | 40 V | 40 V |
| Transition Frequency (fT) | ~300 MHz | ~250 MHz |
| Best Application | Low-power / General Switching | High Current Switching |
MMBT3904 vs BC847 Comparison
Also gives the comparison table for MMBT3904 with BC847 SMD transistor, The table of comparison is given below,
| Feature | MMBT3904 | BC847 |
|---|---|---|
| Transistor Type | NPN | NPN |
| Package | SOT-23 | SOT-23 |
| Max Collector Current (Ic) | Up to 200 mA | Up to 100 mA |
| Collector-Emitter Voltage (Vce) | ~40 V | ~40–45 V |
| DC Current Gain (hFE) | Moderate | Higher (up to ~600) |
| Transition Frequency (fT) | Medium (~300 MHz) | Medium (~100 to 300 MHz) |
| Best Application | Switching, driving loads | Low-noise, small-signal amplification |
| Replacement Suitability | Not always direct replacement | Not always direct replacement |
Conclusion
The MMBT3904 is a popular and widely used SMD transistor in modern electronic circuits. In this article, I have shared with you the comparisons between BC847 and MMBT2222A NPN transistors. But they are not always directly interchangeable due to differences in current handling and gain characteristics. The MMBT3904 has the collector current up to about 200 mA. So it is suitable for general switching applications.
The BC847 has a 100 mA of collector current. So it is better for low noise and small signal amplification. But the MMBT2222A is designed for higher current applications, and the collector current is about 600 mA to 1 A, so it is the best choice for driving heavier loads and high-current switching circuits.
