The **2SB1197-R** (often marked simply as **B1197**) is a PNP epitaxial planar silicon transistor commonly used in general-purpose switching and amplification circuits. It is designed for medium power and low-voltage applications. --- ### 1. Key Technical Specifications The "R" suffix typically refers to the **hFE (DC Current Gain)** classification, indicating a specific range of gain performance. | Parameter | Symbol | Typical Value | Unit | | :--- | :--- | :--- | :--- | | **Collector-Base Voltage** | $V_{CBO}$ | -40 | V | | **Collector-Emitter Voltage** | $V_{CEO}$ | -32 | V | | **Emitter-Base Voltage** | $V_{EBO}$ | -5 | V | | **Collector Current (DC)** | $I_C$ | -800 | mA | | **Power Dissipation** | $P_D$ | 200 to 500 (Package dependent) | mW | | **DC Current Gain (R Rank)** | $h_{FE}$ | 120 to 270 | - | | **Transition Frequency** | $f_T$ | 100 (Typical) | MHz | --- ### 2. Physical Characteristics & Package The B1197-R is most commonly found in surface-mount packages (SMD), which makes it ideal for compact electronic assemblies. * **Common Package:** **SOT-89** or **SOT-23**. * **Pin Configuration:** 1. **Base (B):** Controls the current flow between Emitter and Collector. 2. **Collector (C):** Connected to the load. 3. **Emitter (E):** Usually connected to the positive supply in a PNP configuration. --- ### 3. Complementary NPN Pair In push-pull amplifier circuits or complementary switching stages, the B1197 (PNP) is often paired with the **2SD1781 (NPN)**. Using complementary pairs ensures symmetrical signal processing. --- ### 4. Typical Applications * **Small Signal Amplification:** Used in audio pre-amps or signal processing. * **Voltage Regulation:** Acts as a pass transistor in low-current linear regulators. * **Switching:** Driving LEDs, small relays, or acting as a logic level shifter. * **Driver Circuits:** Used in the driver stage of power amplifiers. --- ### 5. Identification Tip When reading the component casing, you may see: `B1197` followed by a small `R`. The `R` is crucial because it ensures the gain matches the design requirements of your specific circuit. If replaced with a `Q` or `S` rank, the circuit might behave inconsistently due to different gain levels.