From a 3.3 V or 5 V pin
| Pin | Verdict | Why | In free air |
|---|---|---|---|
| ESP32 · 3.3 V | Works | 150 Ω on the base: up to 140 mA of load at a gain of 10 | 140 mA (pin current) |
| Arduino Uno · 5 V | Works | 220 Ω on the base: up to 173 mA of load at a gain of 10 | 173 mA (pin current) |
In free air at 25 °C, with the junction 25 °C below its 150 °C maximum and θJA 417 °C/W, from a 20 mA pin at the datasheet’s forced gain, and no further than the highest current with a guaranteed saturation voltage.
Specifications
| Type | NPN |
|---|---|
| Package | SOT-23 |
| Maximum voltage | 25 V |
| Maximum current | 500 mA |
| Minimum gain hFE | 120 at 50 mA · 50 at 500 mA |
| VCE(sat), maximum | 0.6 V at 500 mA (IC = 10 × IB) |
| VBE(sat), maximum | 1.2 V at 500 mA (IC = 10 × IB) |
| Thermal resistance | θJA 417 °C/W |
| Maximum junction temperature | 150 °C |
| SMD marking | J3Y |
| Datasheet used | CJ (Changjiang) |
Pinout
| Pin | Function |
|---|---|
| 1 | Base |
| 2 | Emitter |
| 3 | Collector |
Seen from above with the single pin (3) at the top: pin 1 is bottom left, pin 2 bottom right.
Similar parts
| Part | Package | VCE(sat), guaranteed | Max voltage | Max current |
|---|---|---|---|---|
| S8050 | SOT-23 | 0.6 V at 500 mA (IC = 10 × IB) | 25 V | 500 mA |
| 2N2222A | TO-92 | 1 V at 500 mA (IC = 10 × IB) | 40 V | 600 mA |
| 2N3904 | TO-92 | 0.3 V at 50 mA (IC = 10 × IB) | 40 V | 200 mA |
| BC547 | TO-92 | 0.6 V at 100 mA (IC = 20 × IB) | 45 V | 100 mA |
| TIP120 | TO-220 | 4 V at 5 A (IC = 250 × IB) | 60 V | 5 A |
Tips
The base resistor is sized for IC = 10 × IB, the condition of the datasheet’s saturation voltage. A higher gain from the hFE column would leave the transistor half on and hot.
Every coil needs a flyback diode across it, cathode to the positive supply. Without it the voltage spike at turn-off can destroy the transistor at the first switching.
An SOT-23 sheds its heat through the copper on the drain pin: the datasheet figure assumes about 6.5 cm² (1 in²), a bare pad runs much hotter.
Open the calculator →Check the S8050 with your own load, supply, PWM frequency and temperature.
Other transistors
2N2222A 2N3904 BC547 TIP120 2N7000 BS170 AO3400A Si2302 IRLML6344 IRLZ44N IRLB8721 IRF520 IRF540N AO3401A IRF9540N
Frequently asked questions
Does the S8050 work with a 3.3 V ESP32?
Yes, with a base resistor: at the gain of 10 the datasheet uses for saturation, a 20 mA pin drives the S8050 up to 140 mA of load. For more current use a logic-level MOSFET.
How much current can the S8050 switch without a heatsink?
About 173 mA from a 5 V Arduino pin, in free air at 25 °C, keeping the junction 25 °C below its 150 °C maximum (limit: pin current).
What is the S8050 pinout?
SOT-23: 1 base, 2 emitter, 3 collector. Seen from above with the single pin (3) at the top: pin 1 is bottom left, pin 2 bottom right.
Source of the figures: CJ (Changjiang) datasheet (PDF)