Amplifier provides two amplified outputs from a single input signal with complete transformer isolation. It uses modulation techniques to obtain the separated output

Dipple, C. R.

Neff, G. A.

English

NASA Technical Reports Server

July 1967
	
Brief 67-10221 
.. 
AEC-NASA TECH BRIEF H 
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Amplifier Provides Dual Outputs from a Single Source with 
Complete Isolation 
T1 
Input Signal	
i
Modulator From Sensor
Carrier 
Amplifier 
7 Demodulator 	 Output A A	 Output Amplifier 
Demodulator[j
	
j T3 
Drive ______________________________ 
Buffer Amplifier	
Output Amplifier 
Kj 12	 Demodulator	 Output B B 
UL 
The problem: 
To provide a means of obtaining two amplified 
outputs from a single input signal. Complete 
isolation from input to output is required. Also, 
since large differences in ground potentials may 
exist between the outputs, these stages must be 
isolated from one another. Dual outputs from one 
input signal have been used before. Previous
designs, however, utilized one and sometimes 
both outputs in common which would not permit 
grounding of the two outputs at different po-
tentials. 
The solution: 
An amplifier which provides transformer isola-
tion and which uses modulation techniques to 
obtain separated outputs. 
This document was prepared under the sponsorship of the Atomic 
Energy Commission and/or the National Aeronautics and Space 
Administration. Neither the United States Government nor any per-
son acting on behalf of the United States Government assumes any
liability resulting from the use of the information contained in this 
document, or warrants that the use of any information, apparatus, 
method, or process disclosed in this document may not infringe pri-
vately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19670000221 2020-03-11T20:30:02+00:00Z
How it's done: 
A low-level signal from a basic sensor such as 
a thermocouple or strain gage is fed into dif-
ferential input terminals of the amplifier through 
a twin conductor, shielded cable. The signal is 
immediately modulated to achieve an equivalent 
dc signal which is then coupled into a carrier 
amplifier via isolation transformer I. After 
amplification to the desired level, the signal from 
the carrier amplifier is fed into output demodu-
ator A for conversion back to an amplified 
duplication of the original signal. The carrier 
amplifier signal is also fed into demodulator B. 
In this path, however, transformer T2 and buffer 
amplifier Al are added ahead of the demodulator. 
Transformer T2 provides carrier signal isolation 
and buffer amplifier K1 provides impedance iso-
lation to prevent demodulator B from introducing 
spikes back into transformer T2. 
Both demodulator A and demodulator B are 
simultaneously driven through separate isolated 
windings of transformer T3. Output amplifiers K2 
and K3 are included to provide low output 
impedance characteristics and load driving capa-
bility. No conductive paths exist between the 
input terminals and output A, between the input 
terminals and output B, or between output A and 
output B. The level of ground voltages is limited
only by the breakdown voltages of the trans-
formers, which can be controlled at the time of 
transformer production. 
Notes: 
1. In typical use, one output is employed as a 
control signal, while the second provides signal 
monitoring. Adaptations of this method for 
achieving dual isolated outputs may be used in 
devices other than amplifiers. 
2. Inquiries concerning this innovation may be di-
rected to: 
Technology Utilization Officer 
AEC-NASA Space Nuclear Propulsion 
Office 
U.S. Atomic Energy Commission 
Washington, D.C. 20545 
Reference: B67-10221 
Patent status: 
No patent action is contemplated by AEC or 
NASA.
Source: C. R. Dipple
of Westinghouse Astronuclear laboratory

and G. A. Neff
of Neff Instrument Corporation

under contract to

AEC-NASA Space Nuclear Propulsion Office

(N UC- 10056) 
Brief 67-10221	 Category 01


Amplifier provides dual outputs from a single source with complete isolation

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