L 7908 -8V Negative Voltage Regulator IC | TO-220

Description

The L7908 -8V Negative Voltage Regulator IC is a highly reliable three-terminal power management component designed to provide a fixed negative 8-volt DC output. Housed in a standard TO-220 through-hole package, this regulator is an essential building block for hardware engineers and hobbyists who need to design stable "split" or dual-rail power supplies (e.g., +8V, GND, -8V).

Available at Tomson Electronics, the L7908 is capable of delivering up to 1.5A of output current when properly mounted to a heatsink. It is engineered with robust built-in safety features, including internal thermal overload protection, short-circuit current limiting, and output transistor safe-area compensation. This makes it nearly indestructible under standard prototyping conditions and highly favored for powering sensitive analog audio circuits and operational amplifiers.

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Specifications

• Model: L7908 (7908 series)
• Output Voltage: -8V DC (Fixed)
• Maximum Output Current: 1.5A (with adequate heatsinking)
• Maximum Input Voltage: -35V DC
• Package Type: TO-220 (Through-hole)
• Pin Configuration: Pin 1 (Ground), Pin 2 (Input), Pin 3 (Output)
• Built-in Protections: Thermal shutdown, short-circuit current limiting

Datasheet

Download L7908 Datasheet PDF

Applications

• Dual-Rail Power Supplies: Paired with an L7808 (positive +8V regulator) to create a symmetrical split power supply from a center-tapped transformer.
• Audio Amplifiers: Providing clean, stable negative voltage rails required by high-fidelity pre-amps, synthesizers, and operational amplifiers (Op-Amps).
• Analog Instrumentation: Regulating power for sensitive analog measurement sensors that require a stable negative reference voltage.
• Consumer Electronics Repair: Serving as a direct replacement part for faulty negative regulators in older audio-visual equipment.

Frequently Asked Questions (FAQ)

Q: Are the pins on the 7908 the same as the 7808?
A: No! This is a very common mistake. The positive 7808 series uses Pin 1 (Input), Pin 2 (Ground), Pin 3 (Output). The negative 7908 series uses Pin 1 (Ground), Pin 2 (Input), Pin 3 (Output). Wiring a 7908 using the 7808 pinout will destroy the IC immediately.

Q: What is the minimum input voltage required for a stable -8V output?
A: Like most linear regulators, the L7908 has a "dropout voltage" of roughly 2V. This means you must feed it an input voltage of at least -10V (ideally -10V to -15V) to ensure a stable -8V output.

Q: Do I need to use a heatsink with this IC?
A: It depends on your power dissipation. If you are drawing more than a few hundred milliamps, or if there is a large difference between your input voltage and the -8V output (e.g., dropping -24V down to -8V), the IC will generate significant heat. In these cases, bolting a TO-220 aluminum heatsink to the metal tab is highly recommended.

Package Includes

• 1 × L7908 -8V Negative Voltage Regulator IC – TO-220