## Technical Overview of the 2SC5545 Transistor The **2SC5545** is an NPN epitaxial planar silicon transistor specifically designed for high-frequency applications. It is most commonly used in the local oscillator and mixer stages of tuners, particularly for VHF and UHF frequency bands (such as TV or radio tuners). --- ### 1. Key Technical Specifications The following table highlights the absolute maximum ratings and electrical characteristics of the 2SC5545: | Parameter | Symbol | Value | Unit | | :--- | :--- | :--- | :--- | | **Collector-to-Base Voltage** | $V_{CBO}$ | 30 | V | | **Collector-to-Emitter Voltage** | $V_{CEO}$ | 15 | V | | **Emitter-to-Base Voltage** | $V_{EBO}$ | 3 | V | | **Collector Current** | $I_C$ | 50 | mA | | **Collector Dissipation** | $P_C$ | 150 | mW | | **Gain Bandwidth Product** | $f_T$ | 1.8 to 3.5 | GHz | | **DC Current Gain** | $h_{FE}$ | 60 to 180 | - | --- ### 2. Main Features * **High Gain Bandwidth ($f_T$):** With a transition frequency reaching up to 3.5 GHz, this transistor is highly efficient at processing high-frequency signals. * **Low Noise Figure:** It is designed to introduce minimal interference, making it ideal for the input stages of communication equipment. * **Small Package:** Typically found in an **S-Mini (SOT-323)** or similar small-outline package, suitable for high-density surface mount (SMD) PCB designs. * **Excellent Linearity:** Provides stable performance across its operating range, which is critical for oscillator stability. --- ### 3. Common Applications Due to its high-frequency capabilities, the 2SC5545 is utilized in: 1. **VHF/UHF Tuners:** Acting as a local oscillator or signal mixer. 2. **RF Amplifiers:** Small signal amplification in wireless communication devices. 3. **Frequency Converters:** Changing signal frequencies in receiver circuits. --- ### 4. Pin Configuration (Typical SOT-323) ```text [Top View] (3) Collector | +-----+-----+ | | +--+-----+--+ | | (1) Base (2) Emitter ``` --- ### 5. Equivalent/Substitute Parts If the 2SC5545 is unavailable, these alternatives are often considered (though pinouts and exact specs should always be verified): * **2SC5088:** Similar high-frequency NPN transistor. * **BFP193:** High-frequency RF transistor (check voltage ratings). * **2SC5548:** A related variant often used in similar circuits.