Improved circuit provides greater reliability and load-carrying capabilities for monostable multivibrator

Goldman, N. E.

Schaffert, J. C.

English

NASA Technical Reports Server

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FIGURE I 
FIGURE 2
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January 1965
	 Brief 65-10011 
NASA TECH
	
ffN'^ ^]SA^ 
NASA Tech Briefs are issued by the Technology Utilization Division to summarize specific 
technical innovations derived from the space program. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical information, Springfield, Virginia, 22151. 
Circuit Improvement Produces Monostable Multivibrator with 
Load-Carrying Capability
The problem: The circuit shown in figure 1 (U.S. 
Patent No. 3,085,165) is satisfactory for certain appli-
cations of light loading. If one is required to drive a 
heavy load from the cathode of Q 1 , the biasing re-
sistor R2 must be of such a low value that circuit 
efficiency in standby would suffer. The reset capaci-
tor C 2 would have to be so large that circuit cutoff by 
negative transients on the supply bus could occur. 
The solution: Improvement of the circuit to pro-
vide greater reliability and load-carrying capability. 
How it's done: In the circuit shown in figure 2, the 
reset transistor Q 1 and coupling diode D 1 (of figure 1)
have been eliminated. This circuit is inherently insen-
sitive to both positive and negative transients on the 
supply bus. It is more efficient when heavily loaded 
and has essentially zero standby current (the leakage 
current of Q i)• In this circuit, reset is accomplished by 
adding the low impedance output from base 1 of Q2 
to the cathode voltage of Q 1 . This effectively back 
biases Q 1 and reduces the current to a value below its 
holding current. Coupling capacitor C 1 is large 
enough for the time constant R (effective load) X C2 
to sufficiently exceed the turn-off time of Q 1 . A re-
sistance at R 1 of 470K ohms and a capacitance at 
of 100 microfarads give a time interval of approxi-
mately 50 seconds.
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States Govern- 
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes 
any warranty or representation express or implied, with respect to the 
accuracy, completeness, or usefulness of the information contained in
this document, or that the use of any information, apparatus, method, 
or process disclosed in this document may not infringe privately-owned 
rights; or B. Assumes any liabilities with respect to the use of, or for 
damages resulting from the use of, any information, apparatus, method, 
or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19650000011 2020-03-11T17:16:39+00:00Z
Notes: 
1. The circuit has driven loads up to 150 ma over a 
temperature range of —30° to + 80° C. 
2. Inquiries concerning this invention may be directed 
to:
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland, 20771 
Reference: B65-10011
Patent status: NASA encourages the immediate 
commercial use of this invention. Inquiries about ob-
taining rights for its commercial use may be made to 
NASA, Code AGP, Washington, D.C., 20546. 
Source: Justin C. Schaffert and 
Norman E. Goldman 
(GSFC-34A) 
Brief65-1001 1	 Category No. 01


Circuit improvement produces monostable multivibrator with load-carrying capability

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