548 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1951 



which is the same as for the grounded base stage. But if i?i, = 



k = '?"""' ti (32) 



r^ + re — r^ 



1 - « (33) 



= 45.5 ii. 



Thus it is seen that the grounded emitter amplifier can produce quite 

 appreciable current amplification — particularly so when a approaches unity. 

 The input impedance to the stage is 



Ri ==r.-hn+ ^-eCr^ " 'i p ♦ (34) 



re -{- fc - rm + Rl 



When Rl = this reduces to 



R^ = n-\- Te (35) 



- rb+ Te 



1 - « (36) 



= 1440 ohms. 



As Rl increases to infinity, the input impedance decreases to r« + n 

 which, for the numerical example, is 266 ohms. 

 The output impedance is 



Ro ^re+r.-r„.+ '^^" ~_[\ (37) 



re -{- n + Rg 



When Rg — 0, this gives 



Ro = r,- -^ {rm - rj (38) 



re + rb 



L re-\- rb A 



= 1.56 (10)' ohms 

 As Rg increases to infinity, Ro decreases to 



Ro = re -\- re — rm 

 = 0.288 (10)' ohms. 



(39) 



(40) 



