What Is the BC547? NPN Transistor: Pinout (C-B-E) and Uses
The BC547 is a very common, European-origin NPN bipolar transistor (BJT). It is used for small-signal amplification and low-current (≤100 mA, V_CEO 45 V) switching. It is the equivalent of the 2N3904 but its pinout is reversed: TO-92, flat face front, left to right is C-B-E. The A/B/C suffixes indicate different gain grades.
The BC547 is a very common, European-origin NPN bipolar transistor (BJT). It is a standard part for small-signal amplification and low-current switching; it is the equivalent of the American 2N3904 but its pinout is reversed. For the concept, see what is a transistor · what is a BJT.
What is the BC547 used for?
Preamplifiers, driving LEDs/buzzers, low-current relay/switching, oscillators and general-purpose analog circuits. Its PNP complement is the BC557.
BC547 pinout (TO-92) — the REVERSE of the 2N3904
With the flat face toward you, leads down, left to right: C – B – E (Collector, Base, Emitter).
| Lead (from left) | Function |
|---|---|
| 1 | Collector (C) |
| 2 | Base (B) |
| 3 | Emitter (E) |
⚠️ Most common mistake: confusing the BC547 (C-B-E) layout with the 2N3904 (E-B-C). The schematic is the same but the lead order differs.
Key electrical specifications
| Parameter | Typical value |
|---|---|
| Type | NPN BJT |
| VCEO | 45 V |
| IC (max) | 100 mA |
| hFE | ~110 – 800 (by A/B/C grade) |
The BC547A/B/C suffixes indicate different hFE (gain) groups.
As a switch/amplifier
The base is driven through a resistor; as a switch, provide enough base current. To check it: test a transistor with a multimeter.
BC547 equivalents and alternatives
- BC548 / BC549: close members of the same family.
- BC557: the PNP complement.
- 2N3904: the American equivalent (different pinout).
- BC337: higher current (800 mA).
Find it in our catalog
To compare price and stock for the BC547 and its alternatives, use the BC547 search.