MMBT3904 Transistor Pinout, Basic Knowledge, Application and Equivalent

What is MMBT3904 Transistor

BT3904 is a small signal surface mounted NPN transistor, so the collector and emitter will remain open (reverse biased) when the base pin is at ground, and will be closed (forward biased) when providing a signal to the base pin. The maximum gain of BT3904 is 300; this value determines the amplification capability of the transistor. The maximum current through the collector pin is 200mA, so this transistor can’t be used to connect loads that consume more than 200mA. In order to bias the transistor, we must provide current (Ib) to the base pin, which should be limited to 5mA. When this transistor is fully biased, it can allow a maximum of 200mA to flow through the collector and emitter. This stage is called the saturation zone, and the typical voltage allowed to pass through the collector-emitter (Vce) or collector-base ( Vcb) is 40V and 60V, respectively. When removing the base current, the transistor is entirely disconnected. This stage is called the cut-off region. The emitter-base (Veb) voltage can be around 6V.

MMBT3904 Transistor Pinout Diagram

Basic Knowledge of MMBT3904 Transistor Parameters


Collector-Base Voltage (Vcb) is 60V

Collector-Emitter Voltage (Vce) is 40V

Emitter-Base Voltage (Veb) is 6 V

Collector Current is 200 mA

Collector Power Dissipation is 200mW

Junction Temperature is 150 ℃

Storage Temperature -55~+150 ℃

MMBT3904 package dimensions

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.

Vcb and Vce are very high, so it can be used to control voltage loads up to 40V.

MMBT3904 Equivalent NPN Transistors

BC636, BC639, BC549, 2N3904, 2N2222, 2N3055, 2N3906, 2N2369, 2SC5200

By the way, if you want to know more details about MMBT3904, you could refer to datasheet on Seeed Open Parts Library (OPL). Seeed Fusion updates the Seeed OPL regularly, so stay tuned for more new components and modules. By choosing all parts from the Seeed OPL, the entire PCBA production time can be reduced to as little as 7 working days.

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