## Overview of the 2SA1585S-R The **2SA1585S-R** is a high-frequency, low-noise PNP epitaxial silicon transistor. It is primarily designed for use in the high-frequency amplification stages of FM tuners, high-speed switching applications, and low-noise audio pre-amplifiers. ### 1. Key Technical Specifications Below is a summary of the electrical characteristics and absolute maximum ratings for the 2SA1585S-R. | Parameter | Symbol | Rating | Unit | | :--- | :--- | :--- | :--- | | Collector-Base Voltage | $V_{CBO}$ | -30 | V | | Collector-Emitter Voltage | $V_{CEO}$ | -20 | V | | Emitter-Base Voltage | $V_{EBO}$ | -5 | V | | Collector Current | $I_C$ | -50 | mA | | Collector Power Dissipation | $P_C$ | 150 | mW | | Junction Temperature | $T_j$ | 150 | °C | | Storage Temperature | $T_{stg}$ | -55 to +150 | °C | --- ### 2. Performance Characteristics The suffix **"-R"** typically refers to the **hFE (DC Current Gain)** classification. In many Japanese transistor naming conventions, "R" indicates a specific gain range. * **DC Current Gain ($h_{FE}$):** Usually ranges between 40 and 80 (Class R). * **Transition Frequency ($f_T$):** Typically around **400 MHz to 600 MHz**, making it excellent for RF (Radio Frequency) applications. * **Output Capacitance ($C_{ob}$):** Very low, generally around **1.2 pF**, which minimizes signal distortion at high frequencies. --- ### 3. Pin Configuration and Package The 2SA1585S-R is most commonly found in a small surface-mount package (SMT), specifically the **SOT-23** or **SC-59** style. | Pin Number | Function | Description | | :--- | :--- | :--- | | 1 | **Base** | Controls the current flow between Emitter and Collector. | | 2 | **Emitter** | The source of charge carriers (holes for PNP). | | 3 | **Collector** | The output terminal where the current is collected. | --- ### 4. Common Applications Due to its high frequency response and low noise profile, it is used in: 1. **RF Amplifiers:** Small-signal amplification in radio receivers. 2. **Oscillators:** Stable frequency generation in tuning circuits. 3. **High-speed Switching:** Digital logic level shifting where speed is critical. 4. **Low Noise Audio:** Initial gain stages where minimizing "hiss" is necessary. --- ### 5. Complementary Part If you are designing a push-pull circuit or a complementary symmetry amplifier, the NPN counterpart to the 2SA1585S is typically the **2SC4115**.