Harmonic distortion in the junction field-effect transistor with field-dependent mobility

It has been found that a harmonic analysis of the usual power-law transfer characteristic of the JFET does not yield equations which accurately predict the third-harmonic distortion products for short-gate structures. However, if field-dependent mobility in the drain-source channel is taken into consideration in the equations for the drain current, a transfer characteristic is obtained of the form
3Z_{D}(1-e^{-r})/ \Gamma^{2}
, where Z
D
is the normalized channel height and Γ is the field factor. Equations for the distortion products M
2
and M
3
, which are derived from this type of characteristic, accurately predict M
2
and M
3
for actual devices as a function of physical parameters. Lower limits on the values of M
2
and M
3
which can be achieved in a practical JFET are presented.