The **C137E** (often referred to in full as the **2SC137E** or sometimes associated with specific ceramic capacitor markings) is most commonly recognized in electronics as a **NPN Silicon Transistor** belonging to the 2SC series. Below is a technical breakdown of its characteristics and usage. --- ### 1. General Specifications The C137E is typically a low-power, high-frequency transistor used for signal amplification or switching. | Parameter | Value (Typical) | | :--- | :--- | | **Type** | NPN | | **Material** | Silicon (Si) | | **Package** | TO-92 (Standard plastic) | | **Vceo (Collector-Emitter Voltage)** | 25V - 30V | | **Ic (Collector Current)** | 30mA - 50mA | | **hFE (Current Gain)** | 40 - 200 (Varies by grade) | | **fT (Transition Frequency)** | ~150 MHz - 250 MHz | ### 2. Pinout Configuration When looking at the flat side of the TO-92 package with the leads pointing down: 1. **Emitter (E)**: Connects to the ground or negative side in standard NPN circuits. 2. **Collector (C)**: Connects to the load. 3. **Base (B)**: The control pin that triggers the transistor. ### 3. Key Applications Because of its high transition frequency and low noise profile, the C137E is frequently found in: * **RF Amplifiers:** Small-signal radio frequency amplification. * **Oscillators:** Generating high-frequency waveforms in communication devices. * **Signal Switching:** Low-power logic switching in vintage audio or radio equipment. --- ### 4. Alternative Identification: Ceramic Capacitors In some contexts, "C137" may refer to a **Ceramic Disc Capacitor** marking rather than a transistor. If the component looks like a small disc with "137" printed on it: * **137** translates to: **13** followed by **7** zeros in picofarads. * **Value**: 130,000,000 pF or **130µF**. * **Note**: This is an extremely uncommon value for a ceramic disc; usually, "C137" is the manufacturer's part number for a specific tolerance or temperature coefficient. ### 5. Equivalent/Replacement Parts If you are looking to replace a 2SC137E transistor, the following are common substitutes: * **2SC1815** (General purpose, very common) * **BC547** (Note: Pinout may be reversed - E-B-C vs C-B-E) * **2N2222** (Higher current capacity)