PNP transistor · TO-92
S8550 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 S8050: switches the plus side of loads up to 0.5 A at low voltage.
- 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 S8550 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 S8550 take?
From the JCET (Jiangsu Changjiang Electronics Technology) datasheet: S8550 TO-92 Plastic-Encapsulate Transistor (PNP), Aug 2017. Stay well inside these limits: they are the most the part takes, not what it should run at.
Open the JCET (Jiangsu Changjiang Electronics Technology) datasheet (PDF)Pin order by maker
Is every S8550 wired E-B-C?
The JCET S8550 datasheet numbers the legs 1 emitter, 2 base, 3 collector: E-B-C with the flat face toward you, and prints E B C under the flat face in its marking drawing.
Parts with other letters around 8550 are different parts with their own datasheets; the same maker's SS8550, for example, is rated 1.5 A. Read every letter on the part before you wire it.
Also quoted above:
A first circuit
Switch the power to a 3.3 V sensor module
- Supply: the same 3.3 V as the microcontroller. Emitter to +3.3 V.
- Collector to the module's VCC pin; the module's GND to 0 V.
- A 1 kΩ resistor from a microcontroller pin to the base.
- Pin low: about 2.6 mA flows out of the base and the module gets power. Pin high: the module is off and draws nothing, which saves a battery.
The transistor drops about 0.1 to 0.3 V, so the module sees a little under 3.3 V. Check that it still works at that voltage.
S8550 questions
What is the S8550 pinout?
For the JCET S8550, flat face toward you and legs down, from left to right: emitter, base, collector (E-B-C).
What do the B, C and D letters on an S8550 mean?
They are the gain rank from the datasheet: B 85 to 160, C 120 to 200, D 160 to 300 and D3 300 to 400. For switching, any rank works.
Is the S8550 the opposite of the S8050?
Yes, it is the PNP complement: same 25 V and 0.5 A limits and the same E-B-C legs in JCET's datasheets, with currents and voltages the other way round.
Can I use an S8550 in place of a BC557?
In low-voltage circuits, yes, with more current to spare. It is rated only 25 V, and its legs are E-B-C where the BC557 is C-B-E.
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 JCET (Jiangsu Changjiang Electronics Technology) datasheet named above. Last reviewed .