Si4 TrenchFET® Power MOSFETs Vishay / Siliconix Si4 TrenchFET® Power MOSFETs are used for amplifying electronic signals. These devices are available in N-channel, P-channel, and N- and P-channel versions. The Si4 MOSFETs offer different VGS and VDS options and temperature ranges. Vishay / Siliconix Si4 TrenchFET Power MOSFETs operate in an enhancement mode and are used for switching between electronic signals. These surface-mount MOSFETs are 100% Rg and UIS tested.