| | |
Summary: IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 48, NO. 12, DECEMBER 2000 2377
Linearity Characteristics of GaAs HBTs and the
Influence of Collector Design
Masaya Iwamoto, Student Member, IEEE, Peter M. Asbeck, Fellow, IEEE, Thomas S. Low, Craig P. Hutchinson,
Jonathan Brereton Scott, Senior Member, IEEE, Alex Cognata, Xiaohui Qin, Lovell H. Camnitz, Member, IEEE,
and Donald C. D'Avanzo, Member, IEEE
Abstract--Linearity characteristics of GaAs heterojunction
bipolar transistors (HBTs) are studied through measurement
and analysis. Third-order intermodulation distortion behavior of
HBTs is examined on devices with various epilayer designs and
at various bias points, loads, and frequencies. Calculations from
an analytical model reveal a strong bias and load dependence
of third-order intercept point (IP3) on the nonlinearities from
transconductance and the voltage dependence of base-collector
capacitance. However, a simple model is not able to predict the
fine details of IP3 with bias. A large-signal HBT model with
an accurate description of the base-collector charge is shown
to account for the measured trends. The base-collector charge
function accounts for the modulation of base-collector capacitance
with current, electron velocity modulation, and Kirk effect (base
|
