74. N-Channel MOSFET for LED Strip PWM Driver
1. Component Purpose
To control LED strip brightness, the MCU outputs a PWM (Pulse Width Modulation) signal. By varying the duty cycle, the average power to the LED strip changes, controlling perceived brightness.
An N-Channel MOSFET as a low-side switch connects the LED strip’s ground side to GND when ON, completing the circuit. The MOSFET switches much faster than a BJT, has virtually zero gate current, and has very low ON-resistance — making it ideal for PWM switching.
Critical: the MOSFET must be a logic-level type — meaning it turns ON fully with a 3.3V gate signal. Standard MOSFETs need 10V at the gate and would barely turn ON (or not at all) with 3.3V.
Required: N-Channel · Vdss ≥20V · Id ≥2A · Vgs(th) ≤2.5V · Rds(on) ≤200mΩ · SOT-23 · SMD
2. How to Find It on DigiKey
Go to DigiKey.com → Discrete Semiconductor Products → Transistors - FETs, MOSFETs - Single
Apply these filters:
- FET Type → N-Channel
- Technology → MOSFET (Metal Oxide)
- Drain to Source Voltage (Vdss) → 20V or higher
- Current - Continuous Drain (Id) → 2A or higher
- Vgs(th) (Max) → 2.5V or lower
- Rds On (Max) → 200mΩ or lower
- Package / Case → SOT-23-3 (TO-236)
- Part Status → Active
Important: Vgs(th) is the threshold where the MOSFET barely starts to turn ON — it is NOT the voltage for full enhancement. For reliable operation, the gate drive voltage should be at least 2× the Vgs(th). With Vgs(th) ≤2.5V and a 3.3V gate, this condition is tight but acceptable for logic-level FETs.
3. Key Specifications & What They Mean
| Specification | Required | Why |
|---|---|---|
| FET Type | N-Channel | Low-side switch; drain to load, source to GND. |
| Vdss | ≥20V | Must block 12V supply with margin. |
| Id | ≥2A | LED strip draws 1A; 2× margin. |
| Vgs(th) Max | ≤2.5V | Must turn ON fully with 3.3V gate drive. |
| Rds(on) | ≤200mΩ | Low ON-resistance = less heat (P = I²×Rds). |
| Vgs Max | ≥8V | Gate survives voltage spikes safely. |
| Power | ≥300mW | Covers I²×Rds = 1²×0.2 = 200mW + margin. |
| Package | SOT-23-3 | Compact SMD for PCB layout. |
| Temp Range | −55°C to +150°C | Wide range; typical for MOSFETs. |
| RoHS | Yes | Compliance required. |
4. Selecting a Safe, Production-Ready Part
The filtered list will show matching parts. Before you pick one, check: Is it Active? Is stock available? Is the manufacturer reputable? Is a datasheet available?
Full checklist: How to Select a Safe, Production-Ready Component — EWskills Guide