## Detailed Technical Overview: MMBT3904G-AL3-R The **MMBT3904G-AL3-R** is a widely used General Purpose NPN Epitaxial Silicon Transistor. It is the surface-mount (SMD) equivalent of the classic through-hole 2N3904 transistor. --- ### 1. Key Technical Specifications Below are the primary electrical characteristics for this specific part: | Parameter | Symbol | Maximum Rating | | :--- | :--- | :--- | | **Collector-Base Voltage** | $V_{CBO}$ | 60 V | | **Collector-Emitter Voltage** | $V_{CEO}$ | 40 V | | **Emitter-Base Voltage** | $V_{EBO}$ | 6.0 V | | **Collector Current (DC)** | $I_C$ | 200 mA | | **Total Power Dissipation** | $P_D$ | 350 mW | | **DC Current Gain** | $h_{FE}$ | 100 - 300 (at 10mA) | | **Transition Frequency** | $f_T$ | 300 MHz | --- ### 2. Package and Manufacturing Details The suffix and prefix in the part number often denote specific manufacturing traits: * **Package Type:** **SOT-23**. This is a small, three-lead plastic surface-mount package. * **MMBT Series:** Indicates a Surface Mount device (as opposed to the "2N" TO-92 series). * **"G" Suffix:** Usually denotes a **Halogen-Free** and RoHS compliant "Green" device. * **Tape & Reel ("-R"):** Indicates the part is supplied on a reel for automated pick-and-place assembly. --- ### 3. Pin Configuration (SOT-23) The device has three terminals arranged as follows: 1. **Pin 1 (Base):** Controls the flow of current between Collector and Emitter. 2. **Pin 2 (Emitter):** The terminal where current exits (in an NPN configuration). 3. **Pin 3 (Collector):** The terminal where current enters. --- ### 4. Typical Applications The MMBT3904G is highly versatile and found in millions of electronic circuits: * **Switching:** Used as a digital switch to turn on LEDs, relays, or other low-power peripherals from a microcontroller GPIO. * **Amplification:** Small signal amplification for audio or RF signals. * **Signal Processing:** Pulse-width modulation (PWM) drivers and signal inverters. --- ### 5. Complementary Part The PNP (negative) counterpart to this NPN transistor is the **MMBT3906**. They are often used together in push-pull amplifier stages or H-bridge motor drivers.