DUALITY AS GUIDE IN TRANSISTOR CIRCUIT DESIGN 



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of the vacuum tube circuit. The first transistor circuit, 17(b), fails to be a dual 

 in that besides having positive feedback around two stages, it has positive 

 feedback in each stage separately. This is avoided in 17(c) by an isolatinsr 



(a) (b) 



Fig. 14 — Resistance — capacitance coupled amplifier and dual. 



Fig, 15 — Cascaded amplifier and duals. 



transformer. It has been shown nevertheless by practical tests that 17(b) 

 acts as a multivibrator, and is perhaps even a better circuit than the others. 

 It has the interesting characteristic that the two inductors are in parallel, 

 and hence may be replaced by a single inductor. 



One explanation of the operation of a vacuum tube multivibrator is this. 



