N-Channel MOSFET for LED Strip PWM Driver

Question

Problem: N-Channel MOSFET for LED Strip PWM Driver. Solve this hands-on electronics task on EWskills.

Accepted Answer

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

5. Filtered DigiKey Link

➡ View Matching Parts — N-Ch MOSFET, SOT-23, Vgs(th)≤2.5V, Id≥2A, Rds(on)≤200mΩ

74. N-Channel MOSFET for LED Strip PWM Driver