The technology and innovation megatrend is real and a necessary approach to the auto lead companies. Over the past 10 years, the market requirements and customer wants changed to more innovative products. Devices and features electronics remains the biggest enabler of and driver for innovations. And the focus is shifting from single to system innovation, integrating components and technologies. One of the greatest technologies is the solid state relay using field effect transistors, which became feasible switching loads to increase fuel economy and cost reduction.Nowadays there are many types of automotive MOSFET offered in the market with integrated logic circuit able to provide enhanced functions to protect the transistor against over temperature, reverse battery, short circuit in the output, customized current slope control and others. However, those functions have some limitations and deficiencies that require external components to make it works in real vehicle applications.This technical paper aims to analyze each enhanced function of the MOSFET, its limitations and propose external components to complete those functions and some software techniques to accomplish the correct behavior. And additionally, application of this technology inside real cars will be listed and the advantages and disadvantages will be analyzed and described in detail.