DESIGN FACTORS OF THE 1553 TRIODE 



527 



It should be understood that many other factors may have a bearing 

 on ampHfier design, such as power consumption, noise performance or 

 amount of feedback. Where such factors are important, they too must 

 be considered, and frequently appropriate merit figures like plate efficiency 

 or noise figure are useful. 



APPENDIX 2 



The Circuit Capacitance Degradation Factor 



The capacitance degradation factor C-n/iC^i + Cp-i) which applies to 

 both gain-band and power-band products, can be calculated approximately 



5 

 4 



I ' 



z 



-„ 2 



rvj 



Q. 

 O 1.5 



1.0 

 0.8 



0.6 

 O.S 

 0.4 



0.2 

 0.15 



0.1 



1000 2000 3000 4000 5000 



FREQUENCY IN MEGACYCLES PER SECOND 



Fig. A2-1. — Passive circuit capacitance Cps. 



as shown below. As the frequency is varied, this factor changes by con- 

 siderable amounts for the 1553 tube; accordingly, both figures of merit 

 vary with frequency, and design control has been exercised to produce 

 maximum merit around 4000 megacycles. 



The capacitance degradation factor is just the proportion which the 

 active tube capacitance bears to the total capacitance of tube and circuit, 

 and would therefore have a maximum of unity if the circuit passive 

 capacitance were made zero. For the 1553, we may begin by assuming that 

 the plate circuit is to be tuned by a resonant coaxial line. As the fre- 

 quency is lowered the efifective capacitance will be increased, since the 

 line must be lengthened; its variation is shown in Fig. A2-1. 



