Small lightweight multiplexer incorporates IG-FETs /Insulated Gate-Field Effect Transistors/ for all digital logic functions, including the internally generated 3.6-kHz clock. It consists of 30 primary channels, each of which is sampled 120 times per second

Gussow, S. S.

English

NASA Technical Reports Server

October 1967	 Brief 67-10396 
NASA TECH BRIEF
	
/& 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Multiplexer Uses • Insulated Gate—Field Effect Transistors 
The problem: 
To design a highly accurate and reliable multiplexer 
of small size and weight for telemetry applications. 
The multiplexer must repetitively sample up to 234 
separate data lines and time-share them on a single 
output line to allow single-line transmission. 
The solution: 
A multiplexer incorporating IG-FET's (insulated 
gate-field effect transistors) for all digital logic func-
tions, including the internally generated 3.6-kHz 
clock. Transistors of this type are also used for analog 
data switching. 
The multiplexer basically consists of 30 primary 
channels, each of which is sampled 120 times per 
second. Twenty-three data channels may be submulti-
plexed to 10 subchannels, sampled at 12 times per 
second. Four other data channels are sampled at only 
120 times per second. The 3 remaining primary chan-
nels are used for amplitude reference and frame identi-
fication. The multiplexer accepts 0 to +5 volts and 
provides 2 parallel PAM (pulse amplitude modulated) 
wavetrain outputs, one with a 1.2-volt pedestal in-
serted during on time and one without pedestal. An 
internal calibration unit provides calibrated output 
levels equal to percentage values of 0, 25, 50, 75, and 
100 within 0.2 percent of an externally applied voltage
reference. The multiplexer uses 15 different printed-
circuit boards, making a total of 35 boards, each 2 
inches x 1 inch in size. Each board is completely 
encapsulated in epoxy resin. The individual encapsu-
lated boards are stacked to form a compact, rugged 
unit occupying a volume of 29 cubic inches and 
weighing 1.3 pounds. 
Notes: 
1. The high accuracy and low output impedance of 
the multiplexer recommend it for driving either 
modulators or analog-to-digital converters. The 
system can also be used as a general purpose 
multiplexer in any application where time sharing 
or sampling is required. 
2. Inquiries concerning design and performance de-
tails may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B67-10396 
Patent status: 
No patent action is contemplated by NASA. 
Source: S. S. Gussow 
of The Boeing Company 
under contract to 
Marshall Space Flight Center 
(M FS- 13096) 
Category 01 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
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Multiplexer uses insulated gate-field effect transistors

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