Text
+VLOAD ── LOAD ── D (pin 3)
                  2N7002
GND ──────────── S (pin 2)

GPIO ── RG ───── G (pin 1)
                 │
              100 kΩ
                 │
               S / GND

• Pull-down: Start with 100 kΩ from Gate to Source. This is an engineering starting value, not an MDD-required component value. Use a lower resistance if leakage, cable coupling, or fast drain transitions compromise the off state; verify the driver's ability to supply the additional DC current.
• Series gate resistor RG: For a slow GPIO-controlled switch, 100 Ω is a reasonable initial damping value, not a universal requirement. Increase it if needed to meet the GPIO peak-current limit; estimate initial current as Ipeak ≈ VGPIO/(RG + driver output resistance), then check the controller datasheet and switching waveform. A larger resistor reduces gate current but increases switching time and potentially switching loss. See TI External Gate Resistor Selection Guide.
• Gate drive: Use a drive level consistent with the published on-resistance conditions. The MDD maximum RDS(on) is 3.0 Ω at VGS = 4.5 V/ID = 200 mA and 2.5 Ω at VGS = 10 V/ID = 300 mA. Check the actual driver's minimum VOH, not just its nominal supply voltage.
• Inductive load: Add a flyback diode across a relay coil or other inductive load: cathode to +VLOAD, anode to Drain. Choose reverse-voltage and forward/pulse-current ratings for the actual supply and coil current. Do not rely on unspecified repetitive avalanche capability. A diode clamp slows coil release; use an appropriately rated higher-voltage clamp if fast release is required. The broader need to limit turn-off voltage from stored inductive energy is explained in TI's snubber discussion.
• Decoupling: The MOSFET has no supply pin and does not require an IN-pin decoupling capacitor. Put load-supply decoupling/bulk capacitance near the switching-current loop as required by the load and wiring; capacitance is load-dependent, so no universal 1 µF requirement is claimed.
• LED load: If the load is an LED, it still needs a series resistor: RLED = (VLOAD − VF − VDS(on))/ILED. The GPIO controls the gate and does not set LED current directly. No fixed 3.3 V/5 V resistor values can be specified without the LED's VF and target current.

• Confirm the SOT-23 land pattern and pad mapping. Use the MDD outline rather than a package-name assumption; its typical body length is 2.9 mm and its same-side terminal spacing is 1.9 mm. The actual Flux footprint was not geometrically audited in this documentation task.
• Keep the gate-drive loop compact. Place RG near the Gate and the pull-down close to Gate/Source; route the controller's ground reference back to Source without sharing a long load-current return. Short loops reduce parasitic inductance; see TI gate-resistor guidance.
• Size Drain/Source copper for load current and heat. Select trace width from copper thickness, allowable voltage drop, and temperature rise rather than assigning a universal width. Extra copper helps spread heat; narrow thermal-relief spokes can restrict that path, so balance reflow solderability against thermal performance. The 357 °C/W figure is tied to the datasheet's specific test board, not every layout.
• Minimize the switched-load loop. Keep an inductive-load clamp near the load connection/switching loop, and keep the Drain node away from high-impedance analog inputs and the Gate trace. Locate load-rail decoupling to support local current changes, not at the gate.
• No differential-pair rules apply. Gate, Drain, and Source are not a differential interface; do not apply USB-style impedance or pair-length rules. Follow the actual PCB fabricator's solder-mask, pad-clearance, and assembly constraints.

1. Treating threshold voltage as full enhancement—or leaving Gate floating. VGS(th) is measured at only 250 µA, whereas the on-resistance specifications use much higher drive voltages and currents. Use a gate-to-source pull-down and verify performance at the driver's worst-case VOH; TI's guide explains both failure mechanisms.
2. Treating “2N7002” or ID(max) as a universal guarantee. Different manufacturers use different dies, resistance limits, and thermal conditions. This part's catalog metadata already conflicts with its attached sheet. Check actual lot documentation, dissipation, temperature, and inductive turn-off voltage before accepting a substitution or running near a stress limit.

• MDD 2N7002 manufacturer-authored datasheet, V 1.0, five pages, attached to this part: 2407101108_MDD-Microdiode-Semiconductor-2N7002_C472906.pdf. Manufacturer website printed in the document: www.microdiode.com; publication/revision date not stated. The hosting filename date is not treated as a document revision date.
• Nexperia 2N7002BK library-attached manufacturer datasheet: 2304140030_Nexperia-2N7002BK-215_C282405.pdf. Revision/date not extracted. The current manufacturer-hosted PDF was located, but its evidence extraction remained pending after retry; newer-revision specifications were not used as verified evidence.
• onsemi 2N7002L/2V7002L, 2N7002L/D: manufacturer PDF. Search indexed June 2024, Rev. 11; that revision/date was not separately citation-verified, while the pinout, resistance, current, and LT1G packaging claims above were verified from the PDF.
• Texas Instruments, Avoid Common Mistakes When Selecting and Designing With Power MOSFETs, SLPA021: application report, especially sections 4–6 on gate voltage, low-side drive, and gate-to-source resistors. Revision/date not independently verified.
• Texas Instruments, External Gate Resistor Selection Guide, SLLA385A: application brief, Rev. A as identified by the indexed title; publication date not verified.
• Texas Instruments, Snubbing the Flyback Converter: technical article, used for the general inductive turn-off/clamping principle, not as a specific 2N7002 relay circuit reference; publication date not verified.
• LCSC C472906 product listing: links in section 7, unavailable during research. Project identifiers and saved catalog values were read directly from the current Flux project, not treated as manufacturer guarantees.