This application note will compare LDMOS versus GaN for RF power amplifier stages. Basic concepts/approximations used for LDMOS will be shown to hold true for GaN.

A comparison of equivalent output power devices will be done. This comparison will show some of the similarities of GaN and LDMOS. Differences will also be shown. Key difference to be illustrated will be the saturation characteristics of GaN.

Basic characteristics such as ruggedness, stability and combining multiple amplifier stages will also be presented.

Additional properties of GaN that are significantly different than LDMOS will be presented. One of these areas is charge trapping effects, in which the device starts to turn off. Another characteristic of GaN that is significantly different is the behavior of gate current near saturation.