QUARTZ CRYSTAL APPLICATIONS 



181 



3 is in the direction of the smallest piezoelectric effect in Rochelle salt 

 and contributes little to the action. If terminal one to the tapped coil is 

 at the top of the coil, the circuit although employing a three electrode 

 crystal connection, effectively reduces to B in which the crystal is in the feed- 

 back, path from plate to grid. On the other hand, if the tap is effectively 

 at the bottom of the coil, the crystal is between grid and ground and feedback 

 occurs through a distributed capacity from plate to grid. Both of these 



ii ntniiiiiiiiiinniiiiin - II n-iii--ii -III' Ill ' 'i"'i" 'r"i"tt 



■J J z- 



•-~ fn^ri'mij " I 'Imr urn r ir 



/ 



[S',*'' 



i 



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Fig. 1.2 — Ocean contour curves 



circuits B and C are widely used in oscillators of Pierce. Prof. G. W. 

 Pierce published a circuit similar to circuit B, having a two electrode 

 quartz crystal connected between grid and plate.^ 



In 1921, Professor Cady at Wesleyan University first showed* that quartz 



3 "Piezoelectric Crystal Resonators and Crystal Oscillators Applied to the Precision 

 Calibration of Wave Meters," G. VV. Pierce, Amer. Acad, of Arts and Sciences, Oct. 

 1923, 81-106. 



* "The Piezoelectric Resonator" W. G. Cad}', Proc. I. R. E. 1922, 10 83. 



