An improved model of a modified intrinsic equivalent circuit of delta-doped AlGaAs/InGaAs/GaAs HEMT, which incorporates the additional capacitive effect physically present due to delta doping and a feedback resistor between gate and drain, is proposed. Admittance parameters of the device are extracted from circuit analysis and intrinsic circuit elements are presented in terms of real and imaginary parts of the admittance parameters. S parameters are also evaluated over the frequency range 1–26 GHz and show good agreement with experimental data. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 376–379, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10923