PNP transistor · TO-92
2N3906 Pinout
Flat face toward you, legs pointing down, left to right: 1 emitter, 2 base, 3 collector (E-B-C).
The PNP partner of the 2N3904, for switching the plus side of loads up to 200 mA.
- Pin 1: Emitter (E)Goes to the plus supply when the transistor is used as a switch.
- Pin 2: Base (B)The control pin. Pulling a small current out of it, through a resistor, toward 0 V switches it on.
- Pin 3: Collector (C)Goes to the load. Current comes out here and through the load to 0 V.
Check your part before wiring. Read the maker and the full part number printed on it, open that maker's datasheet, or test the legs with a multimeter's diode setting.
PNG 1440 × 1280 pixels, SVG to any size. Both keep the wirecora.com mark along the bottom.
Pinout table
Which leg of the 2N3906 is which?
| Pin | Name | What it does |
|---|---|---|
| 1 | Emitter E | Goes to the plus supply when the transistor is used as a switch. |
| 2 | Base B | The control pin. Pulling a small current out of it, through a resistor, toward 0 V switches it on. |
| 3 | Collector C | Goes to the load. Current comes out here and through the load to 0 V. |
Key ratings
How much can the 2N3906 take?
From the onsemi datasheet: 2N3906 General Purpose Transistors, PNP Silicon. Stay well inside these limits: they are the most the part takes, not what it should run at.
Open the onsemi datasheet (PDF)Pin order by maker
Is every 2N3906 wired E-B-C?
The onsemi datasheet numbers the legs 1 emitter, 2 base, 3 collector: E-B-C with the flat face toward you, the same order as the 2N3904.
The BC557, a PNP for the same jobs, is C-B-E. On a part from an unknown maker, check before you trust the order.
A first circuit
Switch the plus side of an LED from an Arduino pin
- Supply: the same 5 V as the Arduino. Emitter to +5 V.
- LED and a 330 Ω resistor in a row from the collector to 0 V.
- A 4.7 kΩ resistor from the Arduino pin to the base.
- Pin low: about 0.9 mA flows out of the base and the LED lights. Pin high: the base sits at the emitter's voltage and the LED is off.
This works only when the load's supply is no higher than the pin's high voltage. For a 12 V load, add an NPN stage in front.
2N3906 questions
What is the 2N3906 pinout?
With the flat face toward you and the legs down, from left to right: emitter, base, collector (E-B-C). Pins 1, 2 and 3 in the onsemi datasheet.
Why does a PNP switch turn on when the pin goes low?
A PNP transistor turns on when its base is pulled about 0.7 V below its emitter. With the emitter at +5 V, a low pin pulls the base down and switches it on; a high pin lets it go off.
How much current can a 2N3906 switch?
200 mA at most, up to 40 V, and 625 mW of heat in free air.
Can I use a BC557 instead of a 2N3906?
Yes, for small switching jobs up to 100 mA, but the BC557 is C-B-E, so it goes in the other way round.
Can I use this pinout picture?
Yes. Download it as PNG or SVG and use it in notes, lessons or posts. The wirecora.com mark along the bottom stays in the picture.
Pin order and ratings from the onsemi datasheet named above. Last reviewed .