2N7002

The 2N7002 is an industry-standard N-channel enhancement-mode MOSFET universally recognized as one of the most widely used small-signal switching transistors. Available from multiple manufacturers including onsemi, Infineon, Diodes Incorporated, NXP, and others, it provides 60V drain-source breakdown voltage, 115mA continuous drain current, and 7.5Ω maximum on-resistance at VGS=10V. The low gate threshold voltage (1.0V to 2.5V) enables direct drive from 3.3V and 5V microcontroller GPIO pins without additional gate drive circuitry. Housed in a compact SOT-23-3 package, the 2N7002 is ideal for low-power switching, level shifting, and load control in virtually every category of electronic design. Its extremely low cost ($0.027 at volume) and broad multi-source availability make it a default choice for general-purpose MOSFET switching.

Enhancement-Mode Operation

The 2N7002 is an enhancement-mode MOSFET, meaning it is normally off (non-conducting) when VGS = 0V. When the gate-to-source voltage exceeds the threshold voltage (VGS(th), typically 2.1V), an inversion layer forms in the P-type body region beneath the gate oxide, creating a conductive N-type channel between drain and source. Increasing VGS further enhances the channel, reducing on-resistance (RDS(on)) and increasing drain current capability.

Switching Behavior

The low gate charge (approximately 50pC) enables fast switching transitions, limited primarily by the gate driver’s current capability and the gate resistance. Turn-on time is determined by how quickly the gate capacitance can be charged above VGS(th), while turn-off requires discharging the gate below threshold. The low capacitance (Ciss ~50pF) makes switching efficient even at moderate frequencies.

Body Diode

Like all vertical MOSFETs, the 2N7002 has an inherent P-N junction (body diode) between source and drain. This diode conducts when VDS is negative (source higher than drain), providing a path for inductive kickback currents in switching applications. The body diode has a typical forward voltage of 0.9V to 1.2V.

On-Resistance Characteristics

RDS(on) varies significantly with gate drive voltage. At VGS=10V, RDS(on) is specified at 7.5Ω maximum. At VGS=4.5V (typical 3.3V logic high), RDS(on) increases. At VGS=2.5V, it increases further, approaching the threshold region. For reliable low-RDS(on) switching, a gate voltage of 4.5V or higher is recommended.

• Low-side load switching for LEDs, relays, and small motors driven from 3.3V or 5V microcontroller GPIO
• Logic-level signal interfacing and voltage translation between different logic domains
• Battery-operated portable devices requiring compact, low-cost power switches with minimal gate drive
• I2C and SPI bus level shifting where bidirectional open-drain communication needs pull-up to different voltages
• General-purpose digital control circuits where low cost and multi-source availability are critical