Multivibrator circuit provides a low-frequency sine wave output without using a low-frequency power transformer or filter components. This circuit, utilizing two transistors and a magnetic core, represents a reduction in complexity, size, and weight over similar units

Moore, E. T.

Yu, Y.

English

NASA Technical Reports Server

September 1969
	 Brief 69-10480 
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. 
An Unconventional Magnetically-Coupled Multivibrator 
Base	 N3 c,	 Saturable Core 
Winding	 r' 
' a Transistor 
I'— 
0)
1+	 MSin 2lrft 
E	
_•_	
ea	
- Ca	 Modulating Signal
	
Ni 
ff --&] 
	
Input -
	 Resistors Collector Voltage-  
(Or Windings 
T
Transistors) 
	
KRb	
S2
JL
 eb 
	
1Cb	 N2
E
lsolatecd
 
. 
Qb Transistor 
Base Windin 
N4 
Basic Multivibrator Circuit 
This physically simple, highly efficient innovation 
should be interesting to manufacturers of electronic 
power supplies and voltage converters and to technical 
personnel working in the field of static power con-
version. Two primary functions of the multivibrator 
are that the circuit can act as a voltage-to-duty-cycle 
generator for nondissipatively regulated dc to dc con-
verters; and with slight modification, the circuit can 
be used as a high-frequency pulse-width modulator 
for controlling a dc to low-frequency sinusoidal ac
inverter. In addition, the duty-cycle generator is suit-
able for speed control of dc motors, while the pulse-
width modulator, when properly combined with other 
power-handling circuits, can be used as a switching-
mode linear amplifier (the dc- to sinusoidal ac inverter 
is a special case where the signal happens to be a sine 
wave.) 
The basic multivibrator circuit, shown in the figure, 
provides a low-frequency sine wave output without 
using a low-frequency power transformer or filter 
(continued overleaf) 
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.
https://ntrs.nasa.gov/search.jsp?R=19690000466 2020-03-16T18:03:24+00:00Z
components. The circuit utilizes two transistors and a 
magnetic core with a rectangular B-H characteristic, 
representing a reduction in complexity, size, and 
weight over similar units. The semiconductor and 
magnetic elements of the multivibrator are transistors 
Qa, Qb and a saturable core T. Collector windings 
N  and N2 have an equal number of turns; base wind-
ings N3 and N4 are also equal. Any number of iso-
lated windings, such as N5, can be provided for multi-
ple outputs. The direct voltage supplying power to the 
two halves of the multivibrator is obtained by dividing 
the input voltage E into two components, ea and e. 
The division of voltage is accomplished through Ca 
and Cb in parallel with Ra and Rb (either resistors or 
transistors); impedances can be held fixed or varied 
through standard control techniques. With Si closed 
and S2 opened, the circuit performs the function of a 
voltage-to-cycle generator. With SI opened and S2 
closed and with Ra =Rb and Ca =Cb, the circuit per-
forms the functions of a pulse-width modulator with 
the sinusoidal reference M Sin 2r ft serving as a mod-
ulating signal. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Headquarters 
National Aeronautics and Space Admin. 
Washington, D.C. 20546 
Reference: TSP69- 10480 
Patent status: 
No patent action is contemplated by NASA. 
Source: Yuan Yu and Edward T. Moore of 
Duke University 
under contract to 
NASA Headquarters 
(HQN- 10226)
. 
Brief 69-10480	 Category 01


An unconventional magnetically-coupled multivibrator

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