3<>4 



BELL SYSTEM TECHNICAL JOIRXAL 



ended type of power transistor using t^\-o gerniaiuum wafers witli a, common 

 radiator for push-pull applications. 



Other Largic-Sigxal Applications 



The static characteristics can be used for calculations of many large- 

 signal circuits of which only a few examples can be given here. The first is a 

 tickler feedback oscillator of Fig. 26, which uses the grounded-base circuit 

 with a resonant circuit in the collector lead, transformer-coupled back to 

 the emitter. 



Other circuits making use of the special possibilities of the transistor 

 include an oscillator with anti-resonant circuit in the base lead, or with a 



:b) 



r 



X 



-^wy^ 



(c) 



Fig. 26 — Transistor oscillators. 



series resonant circuit from collector to emitter. Some of these circuits make 

 use of the short-circuit instability peculiar to the transistor and accordingly 

 would not work with electron tubes. 



Noise 



A discussion of small-signal amplifiers would be incomplete without 

 some mention of the limiting factor of noise. The noise has been left to 

 the last, however, because its discussion complicates the circuits slightly, 

 and perhai^s because it is not well to present too early an aspect of per- 

 formance which is at the moment so much inferior to electron tubes. 



On the circuit representation of noise as well as signal much work has 

 been done by L. C. Peterson.^ It turns out that in the general four-terminal 

 network in which we are interested, a complete noise representation for 



' "Signal and Noise in .Microwave Tetrode," Proc. LR.E., Nov. 1947, pp. 1264-1272. 



