TIP122 NPN Darlington Power Transistor (TO-220)

Prototyping and Engineering Tips from Robogears

• The "Low-Side" Switch: In most Arduino projects, connect the Emitter to Ground, the Collector to your load (motor/LED), and the Base to your digital pin via a $1k\Omega$ to $2.2k\Omega$ resistor.

• Heatsink Necessity: While the TIP122 can handle up to $5A$, it will generate significant heat at high currents due to its higher saturation voltage ($\sim 2V$). If your load exceeds $1A$ to $2A$ continuously, always attach a small U-shaped or finned aluminum heatsink.

• Driving Inductive Loads: Although there is an internal diode, we strongly recommend adding an external "Flyback" diode (like 1N4007 or 1N5408) directly across your motor or solenoid. This protects the transistor from the massive high-voltage spikes generated when the magnetic field collapses.

• PWM Dimming: The TIP122 responds well to PWM (Pulse Width Modulation) for controlling motor speed or LED brightness. However, avoid very high frequencies ($>20kHz$) to minimize switching losses and heat.

Package Includes

• 1 x TIP122 NPN Darlington Power Transistor (TO-220)

Disclaimer

Always calculate your total power dissipation ($P = V_{CE(sat)} \times I_C$) to ensure it stays within the limits of your heatsink. Ensure correct pin orientation before powering up, as reversing the Collector and Emitter under load can cause immediate component failure.