Unified analytical model of HEMTs for analogue and digital applications

A unified model for the I-V characteristics of HEMTs valid for the subthreshold, linear and saturation regions of operation is presented. There is a smooth transition in the current from subthreshold to above threshold and also from linear to saturation. This results in highly continuous channel conductance (gds) and transconductance (gm), which are important circuit parameters in small signal analysis. Comparisons with experimental data show that the model is accurate and valid over a wide range. Further, it is established that the model holds good promise for analogue circuit design by subjecting it to a few benchmark tests. In addition, the model, which was originally developed for n-channel HEMTs, has been suitably modified to predict the I-V characteristics of p-channel HEMTs as well. Finally, an inverter circuit using p-channel HEMT as load and n-channel HEMT as driver has been successfully simulated using the circuit simulator SABER and the nature of the inverter characteristics are found to agree well with the experimental results. © IEE, 2005.