PROPERTIES AND APPLICATIONS OF fl-p-fl TRANSISTORS 555 



For Rg = 0, this reduces to 



Ro=^u^-n^^ (57) 



(58) 



(59) 



- Te -{- n {i — a) 



= 31.1 ohms. 

 For Kg infinite 



Ro=re-\-rc — fm 

 = 0.288(10)« ohms. 

 The matched input impedance is 



Ri« = (n + re) a/-^ + , ,,J:\, -i (60) 



= Vre[rt + r./(l - a)] 

 = 139,000 ohms. 

 The matched output impedance is 



(61) 



Rom — {re -{- fc — fm) A/ , f" 7 j v. " 1 T 



V n+ re {rb + re) (r^ + re - r„) 



= (!-«) Vrc[r6 + rj{\ - a)] 

 = 2990 ohms. 



(62) 

 (63) 



With matched impedance, the maximum available gain of the grounded 

 collector stage is 



(r5 + re){re + fc - r^) 

 M.A.G. = =— (64) 



L^ "^ T '^TTTc "^ (r6+ re)irl+ r, - rjj 

 As a approaches unity, this approaches approximately 



M.A.G. = Te/^fe (65) 



but so long as re <3C re — r,„ , a good approximation is 



M.A.G. = 1/(1 - a) 



(66) 

 = 46.5 or 16.7 db. 



