From a 3.3 V or 5 V pin
| Pin | Verdict | Why | In free air |
|---|---|---|---|
| ESP32 · 3.3 V | Not guaranteed | nothing guaranteed below 10 V | — |
| Arduino Uno · 5 V | Not guaranteed | nothing guaranteed below 10 V | — |
In free air at 25 °C, with the junction 25 °C below its 150 °C maximum and θJA 357 °C/W, at the guaranteed RDS(on) raised with temperature.
Specifications
| Type | N-channel MOSFET |
|---|---|
| Package | TO-92 |
| Maximum voltage | 60 V |
| Maximum current | 500 mA |
| Threshold VGS(th) | 0.8 … 3 V |
| RDS(on), maximum | 5 Ω at 10 V (200 mA) |
| Gate voltage limit | ±20 V |
| Thermal resistance | θJA 357 °C/W |
| Maximum junction temperature | 150 °C |
| Datasheet used | onsemi |
Pinout
| Pin | Function |
|---|---|
| 1 | Drain |
| 2 | Gate |
| 3 | Source |
Flat face toward you, leads down: pin 1 is on the left.
Similar parts
| Part | Package | RDS(on) at 3.3 V | RDS(on) at 5 V | Max voltage | Max current |
|---|---|---|---|---|---|
| BS170 | TO-92 | no | no | 60 V | 500 mA |
| 2N7000 | TO-92 | no | 5.3 Ω | 60 V | 200 mA |
| AO3400A | SOT-23 | 48 mΩ | 32 mΩ | 30 V | 5.7 A |
| Si2302 | SOT-23 | 75 mΩ | 57 mΩ | 20 V | 2.6 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.
Open the calculator →Check the BS170 with your own load, supply, PWM frequency and temperature.
Other transistors
2N2222A 2N3904 BC547 S8050 TIP120 2N7000 AO3400A Si2302 IRLML6344 IRLZ44N IRLB8721 IRF520 IRF540N AO3401A IRF9540N
Frequently asked questions
Does the BS170 work with a 3.3 V ESP32?
Not reliably: the threshold is at most 3 V, but RDS(on) is guaranteed only from 10 V. It may switch small currents, nothing more is promised. Use a MOSFET guaranteed at 2.5 V such as the AO3400A.
What is the BS170 pinout?
TO-92: 1 drain, 2 gate, 3 source. Flat face toward you, leads down: pin 1 is on the left.
Source of the figures: onsemi datasheet (PDF)