The **79L09G-AB3-R** is a specific part number for a fixed negative voltage regulator. This component is widely used in electronic circuits to provide a stable -9V output from a higher negative input voltage. Below is a detailed breakdown of its specifications, naming conventions, and typical applications. --- ### 1. Key Technical Specifications The 79L09 series is the low-power (100mA) version of the standard 7909 negative regulators. | Parameter | Specification | | :--- | :--- | | **Output Voltage** | -9.0V DC | | **Output Current** | 100mA (Maximum) | | **Input Voltage (Max)** | -30V to -35V | | **Package Type** | SOT-89 (Small Outline Transistor) | | **Operating Temperature** | -40°C to +125°C | | **Polarity** | Negative Voltage Regulator | --- ### 2. Part Number Breakdown (UTC Coding) This part is commonly manufactured by **Unisonic Technologies Co. (UTC)**. The suffix represents the following: * **79L09**: The basic series (Negative regulator, Low power, 9V output). * **G**: Halogen-free and RoHS compliant (Green). * **AB3**: Refers to the **SOT-89** package style. * **R**: Tape and Reel packaging (for automated pick-and-place assembly). --- ### 3. Pinout Configuration Since this is an SOT-89 package, the pinout is standard but crucial to remember because it differs from positive regulators (like the 78L09). | Pin Number | Function | Description | | :--- | :--- | :--- | | **Pin 1** | **GND** | Ground reference | | **Pin 2** | **Input (V_in)** | Unregulated negative input voltage | | **Pin 3** | **Output (V_out)** | Regulated -9V output | > **Note:** The large tab on the SOT-89 package is internally connected to the Input (Pin 2). --- ### 4. Typical Application Circuit To ensure stability and reduce noise, capacitors are required at both the input and output stages. ```text -Vin (Unregulated) ----[ Pin 2 ]-------[ Pin 3 ]---- -9V Out (Regulated) | | [Cin] [Cout] | | GND -------------------[ Pin 1 ]---------+---------- GND ``` * **Cin (Input Capacitor):** Typically 0.33µF (Tantalum or Ceramic) to filter high-frequency noise. * **Cout (Output Capacitor):** Typically 1µF to 10µF to ensure loop stability. --- ### 5. Common Use Cases 1. **Dual Supply Rails:** Used alongside a 78L09 to create a +/- 9V dual power supply for Operational Amplifiers (Op-Amps). 2. **Analog Circuits:** Powering sensitive audio equipment or sensors requiring negative bias. 3. **Communication Gear:** Powering RS-232 line drivers or specific RF modules. ---