Transistor Circuits for Analog and 

 Digital Systems* 



By FRANKLIN H. BLECHER 



(Manuscript received November 17, 1955) 



This paper describes the application of junction transistors to precision 

 circuits for use in analog computers and the input and output circuits of 

 digital systems. The three basic circuits are a summing amplifier, an inte- 

 grator, and a voltage comparator. The transistor circuits are combined into 

 a voltage encoder for translating analog voltages into equivalent time inter- 

 vals. 



1.0. INTRODUCTION 



Transistors, because of their reliability, small power consumption, 

 and small size find a natural field of application in electronic computers 

 and data transmission systems. These advantages have already been 

 realized by using point contact transistors in high speed digital com- 

 puters. This paper describes the application of junction transistors to 

 precision circuits which are used in dc analog computers and in the 

 input and output circuits of digital systems. The three basic circuits 

 which are used in these applications are a summing amplifier, an inte- 

 grator, and a voltage comparator. A general procedure for designing 

 these transistor circuits is given with particular emphasis placed on new 

 design methods that are necessitated by the properties of junction 

 transistors. The design principles are illustrated by specific circuits. 

 The fundamental considerations in the design of transistor operational 

 amplifiers are discussed in Section 2.0. In Section 3.0 an illustrative 

 summing amplifier is described, which has a dc accuracy of better than 

 one part in 5,000 throughout an operating temperature range of to 

 50°C. The feedback in this amplifier is maintained over a broad enough 

 frequency band so that full accuracy is attained in about 100 micro- 

 seconds. 



The design of a specific transistor integrator is presented in Section 



* Submitted in partial fulfillment of the requirements for the degree of Doctor 

 of Electrical Engineering at the Polytechnic Institute of Brooklyn. 



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