1074 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1954 



In addition to the transformation term there is also, as shown in Fig. 

 14(b), a series term, 2Rp divided by 1 + M- Here Rp is the plate resistance 

 of the tube, and m is the voltage gain as mentioned before. The factor 2 

 results from the use of two tubes in push pull. If m is large compared to 

 unit}' then this series term becomes approximately 2Rp/n. It is entirely 

 dependent upon the characteristics of the electron tube. As the char- 

 acteristics change from tube to tube with manufacturing variation or 

 in the same tube over a period of time or with variation in batterj- supply 

 potential, the term 2Rp/{l + n) will change accordingly. Percentage- 

 wise this change may be large. This is the largest source of variation in 

 the E2 converter. It can be minimized by operating the converter be- 

 tween impedances much larger in magnitude than 2Rp/{\ + /x) so that 

 variations in this term have relatively small effect. This has been done 

 in the E2 repeater by stepping up the impedance of the transmission 

 line by about 1:9 by means of the transformer shown in Fig. 14. 



THE E3 CONVERTER 



Theoreticallj^, the same converter used for the E2 and shown in Fig. 

 14 could have been used for the E3. Instead of connecting the line to 



AW 



REPEATER 

 NETWORK 



AV^ 



(a) 



a = RESISTANCE 



C = RESISTANCE 



b = OUTPUT IMPEDANCE 

 OF AMPLIFIER 



jj, = RATIO OF OPEN CIRCUIT OUTPUT 

 VOLTAGE TO INPUT VOLTAGE 

 OF AMPLIFIER 



/3,= ^ 



a +b-i-c 



/32 = 



(b) 



a + b + c 



Fig. 15 — E3 Converter; (a) schematic and (b) equivalent circuit. 



