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THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1951 



shown and the voltages V2 and jjlIiZn will have the polarities shown. For 

 the moment it will be assumed that the input impedance of amplifier A 

 is infinitely high, an assumption which will be modified later to agree with 

 actual circuits. The symbols Zn and Zi represent impedances, Rp represents 

 the plate resistance of the output tube {T2) and tiliZw represents the voltage 

 produced in the plate circuit of the output tube of amplifier A, the tube 



Fig. 3 — Latour's circuit. 



7*2 of Fig. 3(a), by the voltage drop IiZn across the input, grid to cathode of 

 Ti, Fig. 3(a). The mesh equations for Fig. 3(b) can be written as follows: 



Vi = {Zu + Zi) 7, -Z1/2 



= - (Zi + nZ^) h + {Rv + ^1) h 



The current h becomes: 



V,{Rp + Zi) 



{Zs + Z,){Rp + Zi) - (Zi + ixZ^)Z, ^^- ^^^ 



The impedance seen looking into terminals 1 and 2 caA be written: 



Z12 = 



