The **2SC5091-R** is a high-frequency NPN epitaxial silicon transistor specifically designed for low-noise amplification in the VHF to UHF frequency ranges. It is commonly used in RF (Radio Frequency) applications such as cellular phones and tuners. --- ### 1. Key Technical Specifications The "R" suffix typically refers to the **hFE (DC Current Gain) classification**, which usually falls within the range of 100 to 200 for this specific model. | Parameter | Symbol | Rating | Unit | | :--- | :--- | :--- | :--- | | Collector-Base Voltage | $V_{CBO}$ | 15 | V | | Collector-Emitter Voltage | $V_{CEO}$ | 7 | V | | Emitter-Base Voltage | $V_{EBO}$ | 1.5 | V | | Collector Current | $I_C$ | 40 | mA | | Collector Power Dissipation | $P_C$ | 100 | mW | | Transition Frequency | $f_T$ | 10 (Typ.) | GHz | | Noise Figure | $NF$ | 1.3 (Typ.) | dB | --- ### 2. Physical and Package Characteristics The 2SC5091-R is a surface-mount device (SMD), making it ideal for compact modern electronics. * **Package Type:** S-Mini (3-pin), also known as SC-70 or SOT-323. * **Pin Configuration:** 1. **Base** 2. **Emitter** 3. **Collector** --- ### 3. Key Features * **High Gain Bandwidth Product ($f_T$):** With a transition frequency of 10 GHz, it is highly capable in high-speed and high-frequency oscillations. * **Low Noise Figure:** It provides excellent signal-to-noise ratios, which is critical for the first stage of a radio receiver (LNA - Low Noise Amplifier). * **Small Capacitance:** High-speed switching and minimal signal distortion due to low parasitic capacitance ($C_{re} \approx 0.45\ pF$). --- ### 4. Typical Applications The 2SC5091-R is found in circuits requiring high-frequency stability: 1. **LNA (Low Noise Amplifiers):** Preamplifiers for RF signals in mobile devices. 2. **VCO (Voltage Controlled Oscillators):** Used in frequency synthesis. 3. **RF Mixers:** For converting high-frequency signals to intermediate frequencies. 4. **Satellite Receivers:** Due to its low noise characteristics in the UHF band. --- ### 5. Equivalent/Alternative Parts If the 2SC5091-R is unavailable, common alternatives with similar high-frequency characteristics include: * **BFS17** * **BFP193** * **2SC5088** (Check datasheet for specific gain matching)