MOSFET Switch Design Request
Thought for 3 mins 30 sec
Here’s a solid way to start your 5 V MOSFET switch, plus how to get a G–S–D‑labeled MOSFET or edit one.
Recommended topology for 5 V (with unknown load)
- Default to a low-side N‑MOSFET switch.
- Wiring:
- Load high side to +5 V, load low side to MOSFET drain.
- MOSFET source to GND.
- Logic drive to gate.
- Add a gate-to-source resistor to prevent a floating gate (100 kΩ is a common starting point for high‑impedance enables).
- Add a small series gate resistor (about 100 Ω) to tame edge ringing.
- If the load is inductive (motor, relay, solenoid), add a flyback diode across the load: cathode to +5 V, anode to the load/MOSFET side.
Parts you can use right away
N‑channel SOT‑23, logic‑level (G–S–D labeled in symbol/footprint):
Supporting passives (examples):
- Gate pulldown: RMCF0603FT100K (100 kΩ, 0603)
- Gate series: RC0603FR-07100RL (100 Ω, 0603)
- Flyback diode (if inductive): SS14_R1_00001 (SMA) or PMEG4010BEA,115 (SOD‑323)
How to edit or create a symbol with G, S, D pins (Flux docs)
This is the most relevant entry I found related to the topic (quoted verbatim):
“2- Creating a Symbol
The symbol is the schematic representation of your component. For detailed instructions on creating custom symbols, please refer to our working with symbols tutorial.
Key aspects of symbol creation include:
- Designing a clear, recognizable shape
- Properly positioning pins
- Adding labels and designators
- Following industry standard conventions when possible
3- Creating a Footprint
The footprint defines the physical layout of your component on the PCB. For detailed instructions on creating custom footprints, please refer to our working with footprints tutorial.”
Source
Next info I need to finish the design for you
- Max load current (peak and average)?
- Gate drive voltage (3.3 V logic or 5 V)?
- Load type (resistive or inductive)? If inductive, what kind?
Once you share those, I can size the passives and finalize the MOSFET choice.
3.3V for the gate drive voltage and resistive load type
Thought for 1 min 31 sec
I’ll build a 5 V low-side MOSFET switch driven by a 3.3 V control signal.
Plan:
- Add a logic‑level N‑MOSFET plus gate series and pulldown resistors.
- Wire: +5V→LOAD→Drain; Source→Ground; IN→series R→Gate; pulldown Gate→Ground.
- Ensure G–S–D labeling and footprint pin mapping match.
- Name nets and update the project description.
- Run ERC/DRC and availability checks.
Click Start to execute, and share your max load current if you know it.
Specify load current
Pick resistor values
Prefer footprint
Ask about P-channel vs N-channel
Flux wiring question
Line: 70:9: Type '{ type: "mosfet"; version: "v2"; pmos: true; threshold: number; transconductance: number; bulkThreshold: number; surfacePotential: number; drainResistance: number; sourceResistance: number; gateTerminalUid: string; drainTerminalUid: string; sourceTerminalUid: string; }' is not assignable to type 'Mosfet2SimulationModelConfig'.
Object literal may only specify known properties, and 'threshold' does not exist in type 'Mosfet2SimulationModelConfig'.
