A simple derivation of field-effect transistor characteristics
In the conventional treatment of the field effect 
transistor, the first step is the specification 
of an impurity profile that describes the 
nature of the gate-channel contact. Solutions 
for the static and small-signal characteristics 
are then valid only for the particular 
impurity profile chosen, and must be repeated 
from the beginning for different 
structures. 
 
The purpose of this communication is to 
present a simple, though approximate, 
development of the characteristics of an 
FET without specifying the detailed nature 
of the structure. The charge-control approach is used, and it is shown that in the pinch-off region the relation between the drain current and the gate-source voltage is 
approximately square law. The results are 
applicable to all gate-channel structures, 
including the insulated gate types.
Approximation of junction field-effect transistor characteristics by a hyperbolic function
To analyze nonlinear circuits using the junction field-effect transistor (JFET), a new empirical equation is proposed to relate drain current to drain-source and gate-source voltages. This equation is a simpler form than the Shockley equations, and requires only drain characteristics to evaluate the constant /spl alpha/ in this equation. Good agreement is obtained between the predicted and experimental results.
Calculation of and Errors in the Susceptibility
The measurement of the susceptibility requires three measurements, two of which have to be performed with a substance of known susceptibility. The difference of these last two measurements furnishes the proportionality constant of the apparatus, always employing the same volume, while the difference with the unknown substance gives the required susceptibility.