The Problem :

Using an N-channel MOSFET as a high-side switch can be tricky. The gate voltage must be higher than the source (which is tied to your load), or the MOSFET won’t turn on fully. This confuses many beginners who expect the same behavior as in low-side switching.

The Solution :

To drive a high-side N-MOSFET properly, you need a gate driver IC that can boost the gate voltage above the source. Another method is using a P-MOSFET, but it requires inverted logic and can be less efficient for higher currents.

Practical Example :

Let’s say you want to switch a 12V LED strip from an ESP32 (3.3V GPIO). A low-side N-MOSFET won’t work if the LED’s common is grounded. Instead, use a bootstrap-based high-side driver with an N-MOSFET to ensure proper switching.

Sample Calculation :

Assume your MOSFET has a gate threshold of 2.5V.

You’ll need at least 12V + 5V = 17V gate drive using a charge pump or driver IC like IR2110.

Product Suggestions :

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• MOSFET

• Gate Driver IC

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