Device has been developed for use in pulse-height analyzer of gamma-ray telescope. Unit shows integral linearity of 0.05 percent and differential linearity of less than 2 percent

Lucas, C. H.

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SI
October 1975	 B75-10277 
NASA TECH BRIEF 
NASA Pasadena Office 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Highly-Stable Analog-to-Digital Converter 
A highly-stable, 13-bit analog-to-digital converter 
(ADC) has been developed for use in a pulse-height 
analyzer of a gamma-ray telescope. Four units are 
currently working in a balloon-borne telescope 
system. When tested, these units showed an integral 
linearity of 0.05 percent and a differential linearity of 
less than 2 percent. 
A simplified block diagram of the ADC is shown in 
the figure. The input signal is fed to amplifier A1
through switch S 1 at the start of conversion. By 
successive approximation, the logic sets the input to 
the ladder network so that the ladder output voltage is 
just below the input signal. The difference between 
the input and the ladder output is amplified by A 1 and 
stored in the sample-and-hold circuit 1. Next, the 
ladder driver circuitry is stepped so that the output 
increases by one bit and is just above the input signal. 
The difference is again amplified by A I but this time is 
stored in the sample-and-hold circuit 2. 
Simplified Block Diagram of ADC
(continued overleaf) 
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https://ntrs.nasa.gov/search.jsp?R=19750000277 2020-03-19T20:13:54+00:00Z
The output of sample-and-hold 1 through S1 
becomes the input for the second half of the 
conversion. The difference between sample-and-holds 
1 and 2 is the difference between the ladder output 
level just above the input signal and the one just 
below; this difference amplified by A 2 becomes the 
reference voltage for the second half of the conversion. 
The second conversion is then done by successive 
approximation, using the same circuitry as for the 
first. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP75-10277
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Inquiries concerning 
nonexclusive or exclusive license for its commercial 
development should be addressed to: 
Patent Counsel 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Source: Charles H. Lucas of 
Caltech/JPL 
(NPO- 13385)
C 
Categories: lii (Electronics - Components 
and Circuitry) 
03 (Physical Sciences) B75-10277
.


Highly stable analog-to-digital converter

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