Description
The TIP115 is a 60V, 2A PNP Darlington transistor. It is the “little brother” to the higher-current TIP12x series, offering a more compact solution for applications where the load current is relatively low (up to 2A) and the supply voltage is 60V or less.
Key Specifications
| Parameter | Symbol | Rating |
| Collector-Emitter Voltage | $V_{CEO}$ | -60V |
| Continuous Collector Current | $I_C$ | -2A |
| Peak Collector Current | $I_{CM}$ | -4A |
| Collector-Emitter Saturation Voltage | $V_{CE(sat)}$ | -2.5V (at 2A) |
| DC Current Gain | $h_{FE}$ | 1,000 min (at 1A) |
| Power Dissipation | $P_D$ | 50W |
Key Characteristics
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PNP Darlington Logic: Like other Darlington pairs, it features two transistors integrated into one package. This gives it a high gain, making it very “sensitive” and easy to switch with low-current inputs.
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High-Side Switching: As a PNP device, it is typically connected to the positive supply rail to switch the load ON/OFF.
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Compact Power: With a 50W power dissipation rating, it is highly capable for small-to-medium loads (like small DC motors, indicator lights, or low-power solenoids) while occupying less space than higher-current alternatives.
Design Considerations
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Voltage Drop: Because of the Darlington configuration, the internal voltage drop is higher than a single BJT. At 2A, the $V_{CE(sat)}$ is 2.5V. This means the transistor will dissipate $2A \times 2.5V = 5W$ of heat. Even at this lower current, a small heatsink is recommended to keep the component cool and reliable.
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Driving from Logic: When switching the TIP115 from a 3.3V or 5V microcontroller, you must remember that the base needs to be pulled close to the positive rail (or significantly below the emitter voltage) to switch. As noted with other PNP transistors, using a small NPN driver transistor is the standard, safest way to ensure the TIP115 switches fully and efficiently.
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Protection: For any inductive load (like a small motor), ensure a flyback diode is placed in parallel with the load to prevent the back-EMF spike from damaging the transistor during power-off events.
Comparison to TIP125
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Current: The TIP115 is rated for 2A, while the TIP125 is rated for 5A.
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Use Case: The TIP115 is ideal for lighter-duty applications where a 5A-rated transistor would be overkill or physically too large for the layout.
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