TIP127 PNP Darlington transistor: specs and pinout
A PNP epitaxial Darlington power transistor in a TO-220 package with built-in base-emitter resistors. The data sheet (onsemi, Fairchild origin) covers TIP125, TIP126 and TIP127; TIP127 is the 100 V part and its complement is the NPN TIP122.
Specs
| Spec | Value | Source |
|---|---|---|
| Collector-emitter voltage (VCEO, TIP127) | -100 V | source Absolute Maximum Ratings (p.1) |
| Collector-base voltage (VCBO, TIP127) | -100 V | source Absolute Maximum Ratings (p.1) |
| Emitter-base voltage (VEBO) | -5 V | source Absolute Maximum Ratings (p.1) |
| Collector current | -5 A DC; -8 A pulse | source Absolute Maximum Ratings (p.1) |
| Base current (DC) | -120 mA | source Absolute Maximum Ratings (p.1) |
| DC current gain (hFE) | 1000 minimum at VCE = -3 V, IC = -0.5 A and at IC = -3 A | source Electrical Characteristics (p.2) |
| Collector-emitter saturation voltage | -2 V maximum at IC = -3 A, IB = -12 mA; -4 V maximum at IC = -5 A, IB = -20 mA | source Electrical Characteristics (p.2) |
| Base-emitter on voltage | -2.5 V maximum at VCE = -3 V, IC = -3 A | source Electrical Characteristics (p.2) |
| Power dissipation | 2 W at 25 C ambient; 65 W at 25 C case | source Thermal Characteristics (p.2) |
| Junction temperature | 150 C maximum; storage -65 C to 150 C | source Absolute Maximum Ratings (p.1) |
Power
| Value | Source | |
|---|---|---|
| Supply | Collector-emitter voltage up to -100 V | source Absolute Maximum Ratings (p.1) |
| Current | Collector current up to -5 A DC | source Absolute Maximum Ratings (p.1) |
Pinout
This is a bare transistor, not a module. Pin order is the TO-220 order given on page 1 of the data sheet: 1 Base, 2 Collector, 3 Emitter.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| Base (1) | Base | Leads face front, TO-220 | source p.1 package view | |
| Collector (2) | Collector (also the tab) | source p.1 package view | ||
| Emitter (3) | Emitter | source p.1 package view |
Build with it
Project ideas for the TIP127 PNP Darlington transistor. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- PWM LED dimmer on the high side: The emitter goes to the Uno's 5 V pin and the collector to the LED and its series resistor. A Uno pin through about 1 k to the base turns the transistor on when the pin is low and off when it is high (the emitter is at 5 V, so a 5 V pin gives no base-emitter voltage). Keep the load to an LED or two at about 20 mA each; the drop across the transistor is small at that current. Learning project.
- Measure the Darlington voltage drop: A few LEDs with series resistors form a load of tens of milliamps switched by the TIP127 from the 5 V rail, with the INA219 in the load line. Comparing the INA219 bus voltage with the 5 V rail shows the saturation drop the sheet quotes (-2 V maximum at -3 A, much less at this current). Stay well under the -5 A rating. Learning project.
- Active-low indicator panel on a Raspberry Pi 5: The emitter goes to the Pi's 3.3 V pin, so a GPIO pin driven high (3.3 V) gives no base-emitter voltage and the transistor is off, and driving it low turns it on through a base resistor. Keep the total LED current small (a few LEDs at a few mA each) because the Pi's 3.3 V pin is not a power supply. Learning project.
Common mistakes
- Treating the board-pin supply as enough base drive: a Darlington needs a base resistor, and the sheet's saturation figures use IB of only -12 mA at -3 A; base current is limited to -120 mA (source: link, p.1-2).
- Skipping the heat sink: at -3 A the saturation voltage can reach -2 V, which is about 6 W, while the part is rated 2 W free in air and 65 W only with the case held at 25 C (source: link, Thermal Characteristics p.2).
- Expecting a low drop: the Darlington saturation voltage is -2 V to -4 V at -3 A to -5 A, and base-emitter on voltage up to -2.5 V, so it wastes volts at low supplies (source: link, Electrical Characteristics p.2).
Not covered by the official source
- The pinout shows the TO-220 order from the sheet's package view; confirm the orientation against the case before wiring.
- Base-resistor and series-resistor values in the ideas are suggestions, not sheet figures.
Sources
- link (onsemi TIP125/TIP126/TIP127 PNP Epitaxial Darlington Transistor, Rev. 1.1.0, November 2014)