What You Need to Know About the MMBT3904 Transistor
22 January 2024
Ⅱ. What is the pin configuration of MMBT3904?
Ⅳ. Typical circuit schematic of MMBT3904
Ⅵ. Absolute maximum ratings of MMBT3904
Ⅶ. What is the difference between MMBT3904 and MMBT5551?
The MMBT3904 is an NPN-type bipolar transistor commonly used in amplification and switching circuits. In this article, we will introduce it in terms of specifications, principle of operation, application fields, and maximum ratings, and compare it with other models.
MMBT3904 is a commonly used triode with a small package and excellent performance. With a noise figure of just 5dB and a power consumption of 350mW, it proves to be an efficient and reliable component. Particularly noteworthy is its maximum noise value of 5dB, a crucial aspect for applications involving amplifiers, where minimizing unwanted noise is paramount. The versatility of the MMBT3904 is evident in its dual-purpose design, serving as both a general-purpose amplifier and switch. As a switch, it can handle a useful dynamic range extending up to 100mA, while as an amplifier, its capabilities extend up to 100MHz. This makes the MMBT3904 an ideal choice for a broad range of electronic applications, striking a balance between compactness, low noise, and high performance.
Alternatives and equivalents:
• 2N3906
• BSR17A
• MMBT4401
MMBT3904 is packaged in SOT-23. As shown in the picture above, it usually has three pins, namely base, emitter and collector. Its pin names and functions are as follows.
Pin 1 (Emitter): Current flows out through emitter.
Pin 2 (Base): The base is the trigger for the transistor.
Pin 3 (Collector): Current flows in through collector.
• MMBT3904 is manufactured by onsemi.
• It adopts SMD or SMT installation method.
• Its transistor polarity is NPN.
• Its power consumption is 350 mW.
• Its rated voltage is 40 V.
• Its frequency is 300 MHz.
• Its continuous collector current is 200 mA.
• Its operating temperature is -55°C to 150°C.
• The length of MMBT3904 is 2.92 mm, the width is 1.3 mm, and the height is 0.93 mm.
• MMBT3904 belongs to the category of bipolar transistors.
• MMBT3904 has three pins and comes in SOT-23 package and tape & reel packaging.
The schematic depicted above illustrates a standard circuit configuration for the MMBT3904. It portrays a lighting circuit design featuring three LEDs arranged in parallel to series, guaranteeing consistent brightness across all LEDs due to their approximate matching forward voltage. This arrangement ensures the emission of a full-brightness source voltage exceeding 7V when the circuit is powered. At lower VINs, the LEDs are connected in parallel, and conversely, the LEDs are connected in series. The circuit is designed to output light at only 4V. This means that it is well suited for low-voltage applications. In addition, the schematic is suitable for applications that require low time harmonic variation and consistency with TRIAC dimmers. When the other transistors are on, transistors Q1 to Q4 are disconnected and the Schottky diode is disconnected, thus allowing the circuit to operate in parallel. Conversely, with Q5, Q6, Q9, Q10 disconnected and S1 on, the circuit operates in series.
MMBT3904 has a wide range of applications in electronics. It is often used in switching circuits, power management circuits and amplification circuits. The MMBT3904 finds application in smart home devices for enhancing signal strength, effectively amplifying feeble sensor signals to a level suitable for powering subsequent circuits or systems. For instance, in a smart temperature controller, the MMBT3904 can amplify a weak signal from a temperature sensor to operate a display screen or regulate a heating element. In addition, the MMBT3904 is often used in radio frequency circuits, such as radar systems and wireless communication devices, due to its small package and high frequency characteristics. In home appliances, it can be used to implement wireless communication and control functions, such as remote control via Bluetooth or WiFi connection to a cell phone. Finally, the MMBT3904 can also be used as a switch to control the on or off state of other circuits. In smart home appliances, it can be used as a switching tube in low-current application scenarios to control the on-off of electrical appliances. For example, it can control the working status of fan, heater and other components.
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only. Values are at TA = 25°C unless otherwise noted.
Notes：
1. These ratings are based on a maximum junction temperature of 150°C.
2. These are steady-state limits. Fairchild Semiconductor should be consulted on applications involving pulsed or low-duty cycle operations.
MMBT3904 and MMBT5551 are two different types of transistors, which differ in their operating principles, characteristics, applications and other aspects.
MMBT3904 is an NPN-type triode characterized by low noise, high amplification and high switching speed. With a maximum collector current of 200mA, a maximum collector-base voltage of 40V, and a maximum power consumption of 350mW, this component finds widespread application in amplification, switching, and driving circuits. Particularly well-suited for low-voltage, medium-current amplification applications, it serves various electronic needs. When selecting and using it, we need to make sure the parameters meet the application requirements to ensure its stable operation.
MMBT5551 is a PNP type triode. Its polarity is opposite to that of an NPN type transistor, with the emitter in P-type material and the base and collector in N-type material. This triode has a very low saturation voltage, which makes it safer and more reliable for use in low-voltage applications. At the same time, it has a high conversion frequency, which means that it can better resist noise and interference when used in high-frequency applications, making it an excellent performance triode.
Frequently Asked Questions
1. What is MMBT3904?
MMBT3904 is an SMD transistor, available in SOT-23 package. The dimensions of the SOT-23 Package is shown below. Applications of MMBT3904. Drive modules, such as LED drive, relay drive, etc. Amplifier modules, such as signal amplifiers, audio amplifiers, etc.
2. How does the NPN work?
The operation of the NPN transistor is based on the flow of electrons. The electrons flow from the collector to the emitter when the base voltage is less than the collector voltage. This flow of electrons creates a current from the collector to the emitter.
3. What is the replacement and equivalent of MMBT3904?
You can replace the MMBT3904 with 2N3906, BSR17A, KST3904LGEMTF, MMBT4401 or MMBT3904LT1G.
4. What is SMD transistor?
SMD Transistor or Surface Mounted Transistor is an electronic component made up of silicon or germanium. A transistor is a three-layer semiconductor which consists of a very thin central layer of one type of semiconductor material, sandwiched between two relatively thick layers of the second type.
