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.
Direct determination of the pinch-off voltage of a depletion-mode field-effect transistor
A direct method of determining V p for a depletion-mode FET is presented and compared with the values determined from a square-law transfer characteristic, the output characteristic, and the cutoff of drain current. The accuracy of the direct method makes it a useful technique for the screening and matching of devices.
NMR characteristics of intracellular K in the rat salivary gland: a 39K NMR study using double-quantum filtering.
Intracellular K of the perfused rat mandibular salivary gland was measured by 39K NMR spectroscopy at 8.45 T. Multiple-quantum NMR arising from multiple-exponential decay was used to eliminate the resonance due to extracellular K in the perfused gland at 25 degrees C. The resonance due to intracellular K consisted of two Lorentzian signals stemming from the [spin 1/2 to -1/2] coherence (sharp resonance) and the [spin -1/2 to -3/2], [spin 3/2 to 1/2] coherences (broad resonance). The transverse relaxation time (T2) corresponding to the [spin 1/2 to -1/2] coherence was ca. 2.5 ms, and that corresponding to the [spin -1/2 to -3/2], [spin 3/2 to 1/2] coherences was ca. 0.4 ms. The relaxation time of the double-quantum coherence of rank 3 (originating from product operators like Ix2Iz) was determined to be ca. 0.2 ms. These results suggest the possibility of the presence of a single homogeneous population of intracellular K with a correlation time of ca. 2.5 x 10(-8) s and a quadrupolar coupling constant of ca. 1.4 MHz.