# 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)…

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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.

Every value cites its sourceOfficial pinout

[Buy on Compoden](https://compoden.com/products/tip127-darlington-pnp-bipolar-power-transistor-5-0-a-100v-2a)

## 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](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20PWM%20LED%20dimmer%20with%20an%20Arduino%20Uno%20where%20a%20TIP127%20switches%20the%20LED%20supply%20on%20the%20high%20side): 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](https://app.soldr.ai/?prompt=I%20want%20to%20build%20a%20transistor%20drop%20meter%20with%20an%20Arduino%20Uno%20and%20an%20INA219%20that%20shows%20the%20voltage%20lost%20across%20a%20TIP127%20switch): 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](https://app.soldr.ai/?prompt=I%20want%20to%20build%20an%20active-low%20LED%20indicator%20panel%20with%20a%20Raspberry%20Pi%205%20where%20a%20TIP127%20switches%20a%20group%20of%20LEDs%20from%20the%203.3%20V%20rail): 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](https://www.onsemi.com/pdf/datasheet/tip127-d.pdf), 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](https://www.onsemi.com/pdf/datasheet/tip127-d.pdf), 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](https://www.onsemi.com/pdf/datasheet/tip127-d.pdf), 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](https://www.onsemi.com/pdf/datasheet/tip127-d.pdf) (onsemi TIP125/TIP126/TIP127 PNP Epitaxial Darlington Transistor, Rev. 1.1.0, November 2014)