Mosfets

An AEG trigger system passes the full motor current through two small metal contacts inside the gearbox. On a stock rifle with a 7.4V NiMH battery and a basic motor, those contacts handle the load fine for years. Move to an 11.1V LiPo, a high-torque motor, or any kind of upgrade that pulls more current, and the contacts start arcing — small electrical sparks that erode the metal over time until the trigger eventually fails. A MOSFET prevents this by routing the high-current motor signal through a solid-state switch instead, while the trigger contacts only see a tiny signal current that wouldn't arc anything.

Three categories of MOSFET cover the market. Basic MOSFETs (simple trigger protection units) replace the trigger contacts with a solid-state switch — cheapest option, adds trigger longevity and lets you run higher-voltage batteries safely. Active-braking MOSFETs add a feature that brakes the motor at end-of-cycle, preventing the piston from over-traveling — sharper trigger response, no missed semi-auto shots. Programmable trigger boards (GATE ASTER, PERUN, TITAN, Jefftron) are the modern standard — full electronic fire control with burst modes, ROF caps, ramp-up trigger response, smart battery management, and app-based configuration on the premium boards.

Brand-wise, GATE ASTER is the speedsoft standard — Bluetooth configuration via the GCS app, the same firmware family as the GATE PTX HPA pistol. PERUN covers the milsim and skirmish market with V2/V3 boards. TITAN offers similar functionality at a competitive price point. Jefftron is the value-end option that adds active braking. Installation depends on the board — basic MOSFETs are drop-in 10-minute jobs; programmable boards require soldering and gearbox disassembly. For installation, see HPA Tech Service.