TR.\NSISTORS IN SWITCHING CIRCUITS 



1229 



then : 



Vc + lA^c - r'/') = (r,„ + n)!, + (r. + rb)Ic 



(15) 



SUMMARY OP IDEALIZATION OF CHARACTERISTICS 



The resuhs of the ideaHzatioii of Ihe device charactcfistics nw, ,sum- 

 nuuized in Fig. 16. Here are given analytic expressions for the input 

 and ()uti)ut voltages in terms of the ini)ut and output currents; the 

 r(>gi()ns are defined symbolically and by tj^pical values; and an e(iuivalcnt 

 circuit is given. It may be noted that the equivalent circuit is identical 

 to the small-signal equivalent tee, excepting the small dc generator 

 /co(/'c — fc ) which usually may be neglected when dealing with con- 

 temporary point contact transistors. 



To obtain any of the negative resistance characteristics it is only 

 necessary first to solve the two equations simultaneously for the ap- 

 propriate voltage in terms of the appropriate current, and then second 

 to insert into the resultant equation the proper parameter values, 

 region by region, to obtain three equations. These equations, when 

 plotted, result in an idealized characteristic similar in form to that of 

 Fig. 12. A detailed example plus synopsis of the properties of the several 

 connections will be given in the following sub-section. 



i_ 



'e 



-VW 





a- 



Ic 



■^llH 



T" 



Vf = (rf + rt,)lf+rblc 



Ico '''s -50/iA 



Fig. 16 — Broken-liiK; transistor cMHiat ions, rcf^ional parameter values and 

 equivalent tee circuit. 



