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.
An Active FET Receiver Front End Mixer
In many recent receiver designs, the front-end mixer determines the receiver's sensitivity and its susceptibility to distortion from large input signals. Two balanced FET mixers are developed for such an application; a common source configuration and a common gate configuration. Each exhibits a range of 110 dB between the available S+N input power necessary for 10 dD sensitivity and the available input power of a two-tone signal which causes intertnodulation products down 40 dB from the desired signals* An expression for the conversion transconductance of a junction FET used as a mixer is first derived from the device transfer characteristic equation* The advantages of a balanced mixer con figuration are then discussed* A noise equivalent circuit which describes the sources of noise in each of the proposed mixers is developed* This leads to the calculation of noise factor and hence, sensitivity of the common source mixer as a function of R , the generator resistance* The dependence of distortion on R for the common source mi'xer is then found and plotted* A comparison of this plot and the sensitivity vs. R plot shows that the maximum dynamic range results from a choice s of R equal to 200 ohms. The dynamic range of the common gate mixer is investigated and found to be equal to that of the common source mixer. The sensitivity, however, is found to be 6 dB worse.
Optimal Combination and Concentration of Antibiotics in Media for Isolation of Pathogenic Fungi and Nocardia asteroides
Strains of Blastomyces dermatitidis, Sporothrix schenckii, Histoplasma capsulatum, Cryptococcus neoformans, Nocardia asteroides, and Coccidioides immitis were tested for in vitro susceptibility to polymyxin, gentamicin, kanamycin, chloramphenicol, and neomycin at concentrations of 1, 2, 4, 8, and 16 μg/ml. Polymyxin was the most inhibitory and gentamicin was the least inhibitory of the five antibiotics. Two Histoplasma mycelial strains were partially inhibited by 2 and 8 μg of gentamicin per ml and showed at least a 2+ growth at the higher antibiotic concentration. Kanamycin and neomycin produced significant inhibition of N. asteroides but otherwise were noninhibitory. A combination of chloramphenicol and kanamycin, each at 16 μg/ml, and gentamicin, at 4 μg/ml, was noninhibitory to the strains tested except for N. asteroides. Chloramphenicol at 16 μg/ml was not inhibitory for N. asteroides. The results suggest that the optimal antibiotic combination to use in the isolation of fungi and higher bacteria is chloramphenicol, 16 μg/ml, and gentamicin, 4 μg/ml. Addition of sheep blood (5%) had no effect on antibiotic susceptibility of the organisms studied.