MOSFET Switch Design Request

3:30

Considering user request.

Planning component recommendations.

Working with symbols and components.

Planning for user needs.

Deciding between PLAN and CONSULT.

Choosing CONSULT for user needs.

Accessing knowledge base.

Reading docs about How do I edit a component symbol and change or label its pins in Flux, and map symbol pins to footprint pads? Also how do I search the library and inspect pin names (G, S, D) before placing?.

Searching for components.

Searching library for: "N-channel MOSFET SOT-23 logic-level, suitable for 5 V gate drive, low RDS(on), GSD pinout labeled"

Searching library for: "P-channel MOSFET SOT-23 logic-level, suitable for 5 V gate drive, low RDS(on), GSD pinout labeled"

Searching library for: "100k resistor"

Searching library for: "100 ohm resistor"

Searching library for: "Schottky diode 1 A for flyback protection"

Creating search plan for: "N-channel MOSFET SOT-23 logic-level, suitable for 5 V gate drive, low RDS(on), GSD pinout labeled"

Creating search plan for: "P-channel MOSFET SOT-23 logic-level, suitable for 5 V gate drive, low RDS(on), GSD pinout labeled"

Creating search plan for: "100k resistor"

Creating search plan for: "100 ohm resistor"

Creating search plan for: "Schottky diode 1 A for flyback protection"

Searching.

Found 58 results.

Searching: "Schottky diode 1 A for flyback protection"

Found 45 results.

Searching: "N-channel MOSFET SOT-23 logic-level, suitable for 5 V gate drive, low RDS(on), GSD pinout labeled"

Found 55 results.

Searching: "100k resistor"

Searching.

Found 48 results.

Searching: "100 ohm resistor"

Searching.

Found 45 results.

Searching: "P-channel MOSFET SOT-23 logic-level, suitable for 5 V gate drive, low RDS(on), GSD pinout labeled"

Searching.

Found 60 results.

Searching: "N-channel MOSFET SOT-23 logic-level, suitable for 5 V gate drive, low RDS(on), GSD pinout labeled"

Searching.

Found 59 results.

Searching: "N-channel MOSFET SOT-23 logic-level, suitable for 5 V gate drive, low RDS(on), GSD pinout labeled"

Found 52 results.

Searching: "P-channel MOSFET SOT-23 logic-level, suitable for 5 V gate drive, low RDS(on), GSD pinout labeled"

Searching.

Found 88 results.

Searching: "P-channel MOSFET SOT-23 logic-level, suitable for 5 V gate drive, low RDS(on), GSD pinout labeled"

Finished searching for components.

Planning for component queries.

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.

75 days

cornfedjoe

3.3V for the gate drive voltage and resistive load type

75 days

flux

1:31

Planning MOSFET switch.

Querying knowledge base.

Clarifying tool usage.

Recommending components.

Clarifying the plan.

Accessing knowledge base.

Creating the plan summary.

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.

Plan

#Goal

Design and add a 5 V low-side MOSFET switch controlled by a 3.3 V logic signal to drive a 5 V resistive load, ensuring safe default gate conditioning and clear G–S–D symbol/footprint mapping.

#Implementation plan

Select and add the MOSFET: 1.1. Choose a logic-level N‑channel MOSFET that fully turns on at 3.3 V gate drive and supports the load current at a 5 V supply. 1.2. Select a SOT‑23 package with clear G (Gate), S (Source), and D (Drain) pin labeling.
Add supporting resistors: 2.1. Place a series gate resistor between the 3.3 V control signal (IN) and the MOSFET’s gate to limit inrush current. 2.2. Add a pulldown resistor from the gate to ground to ensure the MOSFET remains off in absence of a control signal.
Make the circuit connections: 3.1. Connect the 5 V supply to one terminal of the resistive load (LOAD). 3.2. Connect the other terminal of the LOAD to the MOSFET drain (D). 3.3. Connect the MOSFET source (S) directly to ground. 3.4. Connect the 3.3 V control signal (IN) to the MOSFET gate (G) through the series resistor, and attach the pulldown resistor between the gate and ground.
Label and document: 4.1. Ensure the schematic symbol labels the MOSFET’s pins as G, S, and D clearly. 4.2. Verify that the component footprint matches the SOT‑23 package pinout and update designators as needed.
Validate design: 5.1. Run an ERC/DRC check and verify parts availability for all chosen components.

#Success criteria

The MOSFET switch correctly drives a resistive load using 5 V power controlled by a 3.3 V signal.
All MOSFET pins are clearly labeled G, S, and D in both the schematic symbol and PCB footprint.
Safe defaults are implemented via the series gate resistor and pulldown resistor, and the design passes ERC/DRC checks.

Specify load current

Pick resistor values

Prefer footprint

Ask about P-channel vs N-channel

Flux wiring question

75 days

const gateTerminalUid = "d4705b32-ebd5-e041-cb38-748831726582";
const drainTerminalUid = "b50a105a-0fa7-3419-f176-24e4103e029f";
const sourceTerminalUid = "470f452b-3deb-a180-5510-3fe7b2058e85";
const gateTerminal = flux.getNodeById(gateTerminalUid, "elementTerminal");
const drainTerminal = flux.getNodeById(drainTerminalUid, "elementTerminal");
const sourceTerminal = flux.getNodeById(sourceTerminalUid, "elementTerminal");
const vgs = flux.createOutputNode("Vgate-source");
const vds = flux.createOutputNode("Vdrain-source");
const vs = flux.createOutputNode("Vsource");
const vd = flux.createOutputNode("Vdrain");
const vg = flux.createOutputNode("Vgate");
const drainToSource = flux.createOutputNode("Idrain-source");
const getPropOrDefault = (propName: string, defaultValue: number): number => {
    return Number(flux.properties.find((prop) => prop.name === propName)?.value ?? defaultValue);
}
const thresholdVoltage = getPropOrDefault("Threshold Voltage", -1.5);
const transconductance = getPropOrDefault("Transconductance", 2e-5);
const bulkThreshold = getPropOrDefault("Bulk Threshold", 0);

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'.

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