MOSFETs and ETU units are electronic control systems used in electric airsoft guns to manage the flow of electricity between the battery, trigger, and motor. They improve trigger response, protect electrical components, and allow additional programmable features.

In a traditional AEG, the motor current flows directly through the mechanical trigger contacts. Over time this causes electrical arcing and wear, especially when using high-performance LiPo batteries. A MOSFET reroutes the high current through an electronic circuit instead, significantly reducing stress on the trigger contacts.

MOSFET – electronic power switch

A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) acts as an electronic switch controlling the current between the battery and the motor. At its simplest, a MOSFET protects trigger contacts and improves electrical efficiency.

Typical MOSFET benefits include:

faster trigger response
protection of trigger contacts
improved electrical efficiency
safer operation with LiPo batteries

Many MOSFET units also include additional functions such as active braking, which stops the motor quickly after each shot.

ETU – Electronic Trigger Unit

An ETU (Electronic Trigger Unit) is a more advanced electronic control system that often replaces the traditional mechanical trigger assembly. The ETU reads trigger input via sensors and controls the firing cycle electronically.

Modern ETU systems may provide features such as: