TR.\NSISTORS I.V SWITCHING CIRCUITS 1231 



from variations in the peak point. Thus it is necessary to know the 

 relationsliips which (let(M-mine the currents and voltao;es of the peak 

 and N'alh'N' points in ()i(h'r hrst to achieve a design and second, toestab- 

 Ush controls on tlie proper (le\'ice parameters. 



In this example the emitter nei>;ative i-esistance characteristic will be 

 solved and analyzed. The solutions for the other characteristics follow 

 in the same manner and will be summarized. 



EV.VLUATION' OF P:M1TTEH CH.VR.VCTERISTIC AS AN EX.\MPLE 



To obtain the emitter charactei'istic, it is necessary to solve the two 

 equations of Fig. 16 for T"« in terms of /« . The equations as given are 

 for the short-circuit case. Since the general case will involve external 

 parameters as R^ and Re , the equations will be modified to include 

 these parameters. 



The effects of external parameters may be applied very easily since, 



V\ = F« - IMe (17) 



and 



Vc = Vcc - IcRc (18) 



where T^„ and T^^ are supply voltages; V, and Vc are measured from 

 the appropriate terminal to the far end of the external base resistor. 

 External Rh adds directly to rh . Thus the two equations become: 



F« = (r, + ff. + n + Rb)Ie + (n + Rb)Ic (19) 



Vcc + (re - rc')Ico = 



(rm + n-\- Rb)I, + (n + /?6 + r, + Re)h (20) 



In manipulation of equations (19) and (20) it is often more easy to 

 do so in the functional form, 



Fi = Rnh + RvJ2 (21) 



Vo = Rnh + R22h (22) 



with substitution at the evaluation stage. The R"s here include both 

 device and circuit parameters.* 



Solving equations (19) and (20) simultaneously, the following rela- 



* Here the primes indicate generalized open circuit driving point resistance 

 rather than reference to Region I. The duplication of symbols is regretted. 



