The **2N2907** (often referred to as JS2907 in specific manufacturer catalogs or surface-mount coding) is a widely used **PNP Bipolar Junction Transistor (BJT)**. It is designed for general-purpose low-power switching and amplification applications. It is the PNP complement to the popular **2N2222** (NPN) transistor. --- ### 1. Key Technical Specifications The following table summarizes the absolute maximum ratings and characteristics typical for the 2N2907 series: | Parameter | Symbol | Value | Unit | | :--- | :--- | :--- | :--- | | **Collector-Base Voltage** | $V_{CBO}$ | 60 | V | | **Collector-Emitter Voltage** | $V_{CEO}$ | 40 | V | | **Emitter-Base Voltage** | $V_{EBO}$ | 5.0 | V | | **Continuous Collector Current** | $I_C$ | 600 | mA | | **Power Dissipation (TO-18)** | $P_D$ | 400 - 500 | mW | | **DC Current Gain** | $h_{FE}$ | 100 - 300 | - | | **Transition Frequency** | $f_T$ | 200 | MHz | --- ### 2. Physical Packaging and Variants The "JS" prefix or specific markings often refer to the SMD (Surface Mount Device) versions. * **2N2907:** Usually comes in a **TO-18** metal can package (high thermal durability). * **PN2907:** Usually comes in a **TO-92** plastic package (standard through-hole). * **MMBT2907 / 2F (Marking):** The **SOT-23** surface-mount version used in modern compact electronics. --- ### 3. Pinout Configuration For the standard TO-92 or TO-18 packages, looking at the flat side/tab: 1. **Emitter:** Current exits here (in PNP). 2. **Base:** The trigger for the transistor. 3. **Collector:** Current enters here. --- ### 4. Common Applications The 2N2907 is highly versatile due to its fast switching speeds and decent current handling. * **Switching:** Driving small relays, LEDs, or motors (acting as a high-side switch). * **Amplification:** Used in low-power audio stages or signal processing. * **Complementary Pairs:** Used alongside the 2N2222 in "Push-Pull" amplifier configurations to handle both halves of an AC waveform. * **Pulse Shaping:** Due to its fast transition frequency ($f_T$), it is effective in high-speed pulse circuits. --- ### 5. Basic Example Circuit (Switch) To use the 2N2907 as a switch, the Base must be pulled **low** (relative to the Emitter) to allow current to flow from Emitter to Collector. ```cpp // Schematic Logic // [VCC 5V] ----> [Emitter] // [Signal] ----> [Resistor 1k] ----> [Base] // [Collector] ----> [LED] ----> [Resistor 330] ----> [GND] ```