The **2SC5543** is a high-frequency NPN epitaxial silicon transistor designed primarily for low-noise amplification in the VHF to UHF frequency ranges. It is commonly used in telecommunications and radio frequency (RF) equipment. --- ### 1. Key Technical Specifications Below is a summary of the absolute maximum ratings and electrical characteristics for the 2SC5543: | Parameter | Symbol | Value | Unit | | :--- | :--- | :--- | :--- | | Collector-Base Voltage | $V_{CBO}$ | 20 | V | | Collector-Emitter Voltage | $V_{CEO}$ | 10 | V | | Emitter-Base Voltage | $V_{EBO}$ | 1.5 | V | | Collector Current | $I_C$ | 65 | mA | | Total Power Dissipation | $P_C$ | 150 | mW | | Gain Bandwidth Product | $f_T$ | 12 | GHz | | Noise Figure | $NF$ | 1.1 (at 2GHz) | dB | --- ### 2. Physical Characteristics and Pinout The 2SC5543 is typically housed in a small, surface-mount package (often **SOT-323 / SC-70** or similar), making it suitable for compact PCB designs. * **Type:** NPN * **Package Type:** Super Mini Mold (3-pin) * **Pin Configuration:** 1. **Base** 2. **Emitter** 3. **Collector** --- ### 3. Primary Applications Due to its high gain-bandwidth product ($f_T$) and low noise figure, this transistor is ideal for: * **LNA (Low Noise Amplifiers):** Used in the front-end of receivers to amplify weak signals without adding significant noise. * **VCO (Voltage Controlled Oscillators):** Used in frequency synthesis. * **RF Buffers:** Providing isolation between different stages of an RF circuit. * **Cellular and Cordless Phones:** Signal processing in mobile communication devices. --- ### 4. Implementation Example In a standard common-emitter configuration, the 2SC5543 requires careful impedance matching at the input and output to achieve the rated 12 GHz performance. ```cpp // Basic concept of RF biasing for 2SC5543 // Vcc = 5V // Target Ic = 10mA R_bias = (Vcc - Vbe) / Ib; // Requires consideration of Beta (hFE) which ranges from 50 to 160. ``` ---