Biasing point change during the measurements

[Mabrok]

Hi,
I am using CGH40010F GaN-HEMT transistor provided by Cree company. My selected biasing point during simulation using ADS was VDS = 28 V, VGS = -2.7 V which gives IDS = 200 mA. During the measurements I have biased the device with the same above mentioned VDS & VGS. However, I could not get the required current. I only could get IDS = 200 mA with reduced VGS to be -2.5 V which is different from my biasing point during simulations. Why this happened? Thanks in advanced.

 

[FvM]

Simulation uses typical transistor parameters, actual parameters can be different. Datasheet shows +0.7/-0.8V variation of threshold voltage, expect similar range for quiescent voltage. +0.2 V deviation sounds fair.