PNP transistor · TO-92
BC327 Pinout
Flat face toward you, legs pointing down, left to right: 1 collector, 2 base, 3 emitter (C-B-E).
The PNP partner of the BC337: up to 800 mA in a TO-92 case, for switching the plus side of LED strips, relays and small loads.
- Pin 1: Collector (C)Goes to the load. Current comes out here and through the load to 0 V.
- 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: Emitter (E)Goes to the plus supply when the transistor is used as a switch.
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 BC327 is which?
| Pin | Name | What it does |
|---|---|---|
| 1 | Collector C | Goes to the load. Current comes out here and through the load to 0 V. |
| 2 | Base B | The control pin. Pulling a small current out of it, through a resistor, toward 0 V switches it on. |
| 3 | Emitter E | Goes to the plus supply when the transistor is used as a switch. |
Key ratings
How much can the BC327 take?
From the onsemi (Fairchild) datasheet: BC327 PNP Epitaxial Silicon Transistor (BC327-FCS/D, Rev. 2, January 2024). Stay well inside these limits: they are the most the part takes, not what it should run at.
Open the onsemi (Fairchild) datasheet (PDF)Pin order by maker
Is every BC327 wired C-B-E?
The onsemi (Fairchild) and Diotec datasheets both number the legs 1 collector, 2 base, 3 emitter: C-B-E with the flat face toward you, the same order as the BC337 and the BC557.
The two makers agree on the ratings (−45 V, −800 mA, 625 mW). They differ on the gain groups they sell: Diotec lists -16, -25 and -40, onsemi only plain, -25 and -40. Diotec also sells the BC328, the same part rated only −25 V.
No maker we checked uses another leg order, but some TO-92 parts are E-B-C, so check a part from an unknown maker with a meter's diode test.
A first circuit
Switch the plus side of a 5 V LED strip from an Arduino
- Supply: the same 5 V that powers the Arduino. Emitter to +5 V.
- A short 5 V LED strip (up to about 300 mA) from the collector to 0 V.
- A 270 Ω resistor from an Arduino pin to the base, and a 10 kΩ resistor from the base to +5 V to keep it off while the Arduino starts.
- Pin LOW: about 15 mA flows out of the base, the transistor turns on and the strip lights. Pin HIGH: it goes dark. That is the other way round from an NPN.
A PNP switch is off only when its base is at the emitter's voltage, so the load's supply must be no higher than the pin's high voltage: a 5 V pin cannot turn off a BC327 with 12 V on its emitter. Keep it to about 300 mA without a heatsink, as with the BC337.
BC327 questions
What is the BC327 pinout?
With the flat face toward you and the legs pointing down, from left to right: collector, base, emitter (C-B-E). That is pin 1, 2 and 3 in the onsemi (Fairchild) and Diotec datasheets.
How do I turn a BC327 on?
Put the emitter on the plus supply and pull the base toward 0 V through a resistor. Base at the emitter's voltage: off. Base pulled about 0.7 V below it: on.
How much current can a BC327 switch?
800 mA continuous in both datasheets, 1 A peak at Diotec. Heat sets the real limit: 625 mW in free air, so plan on about 300 mA without a heatsink.
Is the BC327 the PNP version of the BC337?
Yes, it is the PNP complement: the same 45 V and 800 mA limits and the same C-B-E leg order, with every current and voltage the other way round.
What is the difference between the BC327 and the BC328?
The legs and the current are the same. The BC328 is rated only 25 V between collector and emitter, the BC327 45 V.
Can I use a BC327 instead of a BC557?
Yes, in the same holes: both are C-B-E and rated 45 V. The BC327 carries up to 800 mA, the BC557 only 100 mA.
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 (Fairchild) datasheet named above. Last reviewed .