PIEZOELECTRIC CRYSTALS IN OSCILLATOR CIRCUITS 183 



and 



J_ J_ 

 ^ + ^ — coLi 

 coCi coCo 



(12.39) 



a^C( 



-*^o 



"1 1 1 M 



- + ^ + — + 

 Co C4 C(7 Co 



CL - "^v . 



1 + i?p ( — wC2 



.CO/.2 



Fig. 12.16 — Frequency and activity change for variations in the plate circuit 

 capacitance. Crystal connected grid to plate 



There are two values of co which satisfy (12.39) but only one of these co„ 

 will satisfy (12.38). At this value of co„ 



12 



r _ — _ — T 



|_ coCi coCoJ 



Rt « coLi - 



(12.40) 



By introduction of this and the assumption that coo is essentially constant, 



(12.38) may be written 



RiCo 



'1 1 1 M 



~ + — + ^ + 



Co C4 C(7 C(7 



+ 



1 



+ R\ ( - — coo C2 ) 



\COoi>2 / _ 



jT — COo C2 J 



ajoi>2 / 



Rr 



(12.41) 



COoCg 



1 + i?;("7 - C00C2) 



\aJo L2 / 



= 



