The **MMBT3904G-AE3-R** is a widely used General Purpose NPN Bipolar Junction Transistor (BJT) housed in a compact surface-mount package. It is the SMD (Surface Mount Device) equivalent of the classic through-hole 2N3904 transistor. --- ### 1. Key Technical Specifications The following table summarizes the primary electrical characteristics of the MMBT3904G-AE3-R: | Parameter | Symbol | Value | Unit | | :--- | :--- | :--- | :--- | | **Collector-Emitter Voltage** | $V_{CEO}$ | 40 | V | | **Collector-Base Voltage** | $V_{CBO}$ | 60 | V | | **Emitter-Base Voltage** | $V_{EBO}$ | 6.0 | V | | **Continuous Collector Current** | $I_C$ | 200 | mA | | **Power Dissipation** | $P_D$ | 350 | mW | | **DC Current Gain** | $h_{FE}$ | 100 - 300 | (at 10mA) | | **Transition Frequency** | $f_T$ | 300 | MHz | --- ### 2. Package and Pinout Details The "AE3" suffix typically refers to the **SOT-23** package, which is a standard small-outline transistor package with three terminals. * **Pin 1:** Base (B) * **Pin 2:** Emitter (E) * **Pin 3:** Collector (C) --- ### 3. Functional Applications Due to its high switching speed and moderate current handling, this part is used in: 1. **Switching:** Turning on/off small loads like LEDs, relays, or logic gates. 2. **Amplification:** Low-noise signal amplification in audio or RF circuits. 3. **Level Shifting:** Converting signals between different voltage domains (e.g., 3.3V to 5V). --- ### 4. Part Number Breakdown Understanding the nomenclature helps in sourcing or finding alternatives: | Segment | Meaning | | :--- | :--- | | **MMBT** | Surface Mount Bipolar Transistor prefix | | **3904** | Industry standard part number (NPN type) | | **G** | Usually indicates Halogen-Free or Green material | | **AE3** | Package style (SOT-23) | | **R** | Tape and Reel packaging for automated assembly | --- ### 5. Schematic Symbol (NPN) ```text (Collector) | --+-- / | (B) | |--> (Arrow points out for NPN) \ | --+-- | (Emitter) ```