TRANSISTOR CIRCUITS FOR ANALOG AND DIGITAL SYSTEMS 329 



designed to have about 15.6 db less feedback than that shown in Fig. 10 

 since this amount is adequate for the present purpose. 



The bandwidth of the dc ampHfier is only of secondary importance 

 because the phase shifts introduced by the two amplitude selectors in 

 the voltage encoder tend to compensate each other. 



6.3. Experimental Results 



The accuracy of the voltage encoder is determined by applying a 

 precisely measured voltage to the input of the summing amplifier and by 

 measuring the time interval between the two output pulses. The maxi- 

 mum error due to nonlinearities in the summing amplifier and the voltage 

 ramp is less than ±0.5 microseconds for a maximum encoding time of 

 3,000 microseconds. An additional error is introduced by the noise voltage 

 generated in the first transistor stage of the summing amplifier. The 



! RMS noise voltage at the output of the summing amplifier is less than 

 0.5 millivolts. This noise voltage produces an RMS jitter of 0.25 micro- 



I seconds in the position of the second voltage comparator output pulse. 



; The over-all accuracy of the voltage encoder is one part in 4,000 through- 



' out a temperature range of 20°C to 40°C. 



1 

 I 



i ACKNOWLEDGEMENTS 



! 



I The author wishes to express his appreciation to T. R. Finch for the 

 ^ advice and encouragement received in the course of this work. D. W. 

 ! Grant and W. B. Harris designed and constructed the magnettor used 

 ' in the AZS circuit of the integrator. 



I Appendix I 



I RELATIONSHIP BETWEEN RETURN DIFFERENCE AND LOOP CURRENT 

 i TRANSMISSION 



} In order to place the stability analysis of the transistor feedback ampli- 

 fier on a sound basis, it is desirable to use the concept of return differ- 

 ence. It will be shown that a measurable quantity, called the loop current 

 transmission, can be related to the return difference of aZc with reference 

 Ve .*• t In Fig. 24, N represents the complete transistor network exclusive 

 of the transistor under consideration. The feedback loop is broken at 

 the input to the transistor by connecting all of the feedback paths to 



* In this appendix it is assumed that the transistor under consideration is in 

 the common emitter connection. The discussion can be readily extended to the 

 other transistor connections. 



t This fact was pointed out by F. H. Tendick, Jr. 



