79L09 Negative Voltage Regulator TO-92

The 79L09 Voltage Regulator in a TO-92 package is a compact, reliable negative linear voltage regulator designed to deliver a stable -9 V output up to 100 mA. Ideal for building a negative rail in analog circuits, it suits both electronics engineers and hobbyists working with Arduino, Raspberry Pi, and other microcontroller-based electronics modules and components.

Key Features 🔧

• High-precision -9 V output: Provides a steady, uniform negative voltage for sensitive analog and mixed-signal designs.
• Wide operating range: Suitable for a broad spectrum of electronics components, modules, and embedded systems.
• Compact TO-92 package: Through-hole format for easy prototyping, breadboarding, and integration into production PCBs.
• High reliability: Engineered for robust, long-term performance in varied environments.
• Typical protections: Integrated current limiting and thermal shutdown for enhanced safety and durability.

Technical Specifications 📐

• Product Type: Negative linear voltage regulator
• Model: 79L09
• Package Type: TO-92 (through-hole)
• Regulated Output Voltage: -9 V
• Maximum Output Current: 100 mA
• Operating Temperature Range: -40°C to +125°C

Typical Applications 🧰

The 79L09 TO-92 is versatile and well-suited for many designs, including:

• Power supply circuits and negative rail generation
• Motor control systems (logic and analog support)
• Telecommunication devices and line interfaces
• Consumer electronics and audio equipment
• Industrial machinery and instrumentation
• Op-amp biasing and analog signal conditioning
• RS-232/legacy interface support requiring negative voltage

Package & Pinout 🧲

TO-92, 3-pin through-hole package. A common pinout (front/flat side facing you) is:

• Pin 1: Ground
• Pin 2: Input (more negative than ground)
• Pin 3: Output (-9 V)

Important: Pinouts can vary by manufacturer. Always verify against the device datasheet before assembly.

Design Notes & Best Practices 🛡️

• Headroom (dropout): Ensure sufficient input-output voltage differential for regulation; see datasheet for limits.
• Decoupling: Place appropriate input/output bypass capacitors close to the regulator pins per the manufacturer’s recommendations to ensure stability and low noise.
• Thermal considerations: Power dissipation is (|Vin| − 9 V) × Iout. Manage heat accordingly, even in TO-92 packages.
• Polarity: Observe correct negative-regulator wiring to avoid damage to connected electronics components and modules.