THE L3 SYSTEM AMPLIFIERS 



901 



0.3 0.4 0.6 0.8 1.0 2 3 4 5 6 



FREQUENCY IN MEGACYCLES PER SECOND 



Fig. 12 — Relative gain of regulating network for extreme and mid-range ther- 

 mistor settings. 



By using this result in equation (8) expressions for Zi and Zi were ob- 

 tained from which the configuration that is shown in Fig. 11(b) was 

 synthesized. 



Fig. 12 shows the voltage which would be developed across the regulat- 

 ing network versus frequency in response to a constant current driving 

 force, for the mid-range and extreme values of thermistor resistance. 

 The slope across the band for the mid-range value of 7.5 db; this is the 

 regulating network contribution to the total slope of 37 db required of 

 the complete amplifier. 



To the extent that the differences between the curves of Fig. 12 fail 

 to exactly match the desired square-root of frequency characteristic, the 

 action of the regulating network will introduce an equalization error. 

 This regulation error is shown in Fig. 13. It amounts to a few hundredths 

 of a db for a six db gain change, caused in part by network design imper- 

 fections and in part by the fact that very small second order effects 

 result in the amplifier gain not exactly following the regulating network 

 impedance. 



Beta Circuits 



Starting from our basic requirement that a slope of 37 db across the 

 transmitted band must be obtained, and noting that the total of the 

 contributions from the coupling networks and regulating network is 16 

 db, we are left with about 20 db of shaping to be supplied by the beta 

 circuits. The input beta circuit has been designed to supply most of 

 this remainder, the contributions of the output beta circuit and the 

 11/3/(1 — ju/3) effects in the amplifiers being only three db. The original 

 design procedure for this network was basically the same as for the 



