Bidirectional logic-level shifter
A single 2N7000 with two pullup resistors is the classic building block for translating signals (such as I2C or a plain digital line) between a 3.3 V device and a 5 V device in both directions.
2N7000 MOSFET
N-channel enhancement-mode MOSFET in a TO-92 package that switches loads up to 60 V and 200 mA from a logic-level gate signal.
What is the 2N7000 MOSFET?
The 2N7000 is a small-signal N-channel enhancement-mode MOSFET in a through-hole TO-92 package. It is a jellybean part used as a low-side switch and signal buffer: it stays off with no gate voltage and turns on once the gate-to-source voltage rises past its threshold (roughly 0.8 to 3 V). With a 60 V drain-source rating and up to 200 mA of continuous drain current, it comfortably drives small loads that a microcontroller pin cannot handle directly.
Because the gate is high-impedance, the device draws essentially no steady-state current from whatever drives it, so a logic output can switch it with negligible load. On-resistance is low (around 1.2 ohms typical, 5 ohms maximum), but that figure is specified at a gate drive of 10 V. At 5 V it still switches light loads well, and at 3.3 V it is only partially on. Total power dissipation is limited to 400 mW in the TO-92 package.
Typical roles are low-side switching of LEDs, small relays, and buzzers, plus logic-level shifting between voltage domains. For any load drawing more than a couple hundred milliamps, a dedicated power MOSFET is the better choice.
2N7000 MOSFET pinout
| Pin | Function | Type |
|---|---|---|
S Source | Passive | Passive |
G Gate | Analog | Digital input |
D Drain | Passive | Passive |
Specifications
- Dimensions
- 4.5 × 4.5 × 3.5 mm
Verified from the Tinkered component library.
Circuit requirements
- Wire it as a low-side switch: source to ground, the load between the positive supply and the drain, and the gate to your driving signal.
- Drive the gate as high as your logic allows. RDS(on) is specified at VGS = 10 V, so 5 V drive suits light loads, while 3.3 V leaves the channel only partly on with higher on-resistance and more self-heating.
- Add a gate pulldown resistor (about 10 k�011) from gate to source so the MOSFET switches fully off when the driving pin is tri-stated or floating.
- Respect the limits: 200 mA continuous drain current, 400 mW dissipation, and 60 V drain-source. Keep gate-to-source voltage within about plus or minus 20 V.
- When switching an inductive load (relay coil, motor, solenoid), place a flyback diode across the load to clamp the turn-off spike below the 60 V drain-source rating.
- Driving an LED through the drain still needs a series current-limiting resistor; the MOSFET does not limit current on its own.
Common 2N7000 MOSFET mistakes
Assuming a low threshold means fully on at 3.3 V
A threshold near 2 V only means the device starts conducting; the low on-resistance is specified at a 10 V gate drive. Driving the gate at 3.3 V leaves the channel partially on, so it drops voltage and heats up. Give the gate as much drive as your supply allows.
Overloading the tiny TO-92 package
The 2N7000 is rated for only 200 mA continuous and 400 mW dissipation. Trying to switch a motor, a long LED strip, or a large relay overheats and destroys it. Use a proper power MOSFET for higher-current loads.
Leaving the gate floating
The high-impedance gate picks up stray charge and noise, so without a gate-to-source pulldown resistor the MOSFET can switch erratically or stay latched on when the driving pin is not actively low. Always add a pulldown.
Confusing the pinout with the BS170
The 2N7000 and the similar-looking BS170 have mirrored TO-92 pinouts (source and drain are swapped). With the flat face toward you and leads down, the 2N7000 is Source, Gate, Drain from left to right. Verify before inserting.
Omitting a flyback diode on coils and motors
Switching off an inductive load produces a large voltage spike. Without a freewheeling diode across the load, that spike can exceed the 60 V drain-source rating and instantly kill the part.
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