From a 3.3 V or 5 V pin
| Pin | Verdict | Why | In free air |
|---|---|---|---|
| ESP32 · 3.3 V | Works | RDS(on) at most 75 mΩ guaranteed from 2.5 V | 2.3 A (heat) |
| Arduino Uno · 5 V | Works | RDS(on) at most 57 mΩ guaranteed from 4.5 V | 2.6 A (heat) |
In free air at 25 °C, with the junction 25 °C below its 150 °C maximum and θJA 175 °C/W, at the guaranteed RDS(on) raised with temperature.
Specifications
| Type | N-channel MOSFET |
|---|---|
| Package | SOT-23 |
| Maximum voltage | 20 V |
| Maximum current | 2.6 A |
| Threshold VGS(th) | 0.4 … 0.85 V |
| RDS(on), maximum | 75 mΩ at 2.5 V (3.1 A) · 57 mΩ at 4.5 V (3.6 A) |
| Gate voltage limit | ±8 V |
| Gate charge | 5.5 nC at 4.5 V |
| Thermal resistance | θJA 175 °C/W |
| Maximum junction temperature | 150 °C |
| Datasheet used | Vishay (Si2302CDS) |
Pinout
| Pin | Function |
|---|---|
| 1 | Gate |
| 2 | Source |
| 3 | Drain |
Seen from above with the single pin (3) at the top: pin 1 is bottom left, pin 2 bottom right.
Similar parts
| Part | Package | RDS(on) at 3.3 V | RDS(on) at 5 V | Max voltage | Max current |
|---|---|---|---|---|---|
| Si2302 | SOT-23 | 75 mΩ | 57 mΩ | 20 V | 2.6 A |
| 2N7000 | TO-92 | no | 5.3 Ω | 60 V | 200 mA |
| BS170 | TO-92 | no | no | 60 V | 500 mA |
| AO3400A | SOT-23 | 48 mΩ | 32 mΩ | 30 V | 5.7 A |
| IRLML6344 | SOT-23 | 37 mΩ | 29 mΩ | 30 V | 5 A |
| IRLZ44N | TO-220 | no | 25 mΩ | 55 V | 47 A |
| IRLB8721 | TO-220 | no | 16 mΩ | 30 V | 62 A |
| IRF520 | TO-220 | no | no | 100 V | 9.2 A |
| IRF540N | TO-220 | no | no | 100 V | 33 A |
Tips
Keep the 10 kΩ from gate to ground: while the microcontroller boots its pins float and the MOSFET could turn on by itself.
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 Si2302 with your own load, supply, PWM frequency and temperature.
Other transistors
2N2222A 2N3904 BC547 S8050 TIP120 2N7000 BS170 AO3400A IRLML6344 IRLZ44N IRLB8721 IRF520 IRF540N AO3401A IRF9540N
Frequently asked questions
Does the Si2302 work with a 3.3 V ESP32?
Yes: its RDS(on) is guaranteed at 2.5 V (at most 75 mΩ), and a 3.3 V pin is above that. In free air it handles about 2.3 A.
How much current can the Si2302 switch without a heatsink?
About 2.6 A from a 5 V Arduino pin, in free air at 25 °C, keeping the junction 25 °C below its 150 °C maximum (limit: heat).
What is the Si2302 pinout?
SOT-23: 1 gate, 2 source, 3 drain. Seen from above with the single pin (3) at the top: pin 1 is bottom left, pin 2 bottom right.
Source of the figures: Vishay (Si2302CDS) datasheet (PDF)