Two-transistor multivibrator has minimum power dissipation and maximum reliability. It minimizes the use of components that are subject to environmental changes or other unpredictable behavior

Kleinberg, L. L.

Lavigne, R. C.

English

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May 1966	 Brief 66-10179 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Complementary Monostable Circuits Achieve Low Power Drain and 
High Reliability
The problem: 
To design a complementary monostable multi-
vibrator having minimum power dissipation and 
maximum reliability. 
The solution: 
A two-transistor multivibrator that minimizes the 
use of components that are subject to environmental 
change or other unpredictable behavior. The circuit 
has virtually no power drain in standby operation. 
How ifs done: 
The two transistors are normally off in the absence 
of a biasing network to turn them on. When a positive
trigger pulse is applied to the input coupling network 
(C 1 , R6 , Di ), both transistors turn on. Positive re-
generation occurs because the input trigger pulse is 
amplified by the forward voltage gain [I + R2/R11 
of the circuit and fed back through C2 to the base of 
Q' in phase with the input trigger pulse. If the attenua-
tion of the amplified trigger pulse, approximately 
equal to [ R4 /R3
 + R4 1, is small, regeneration is 
rapid. Q2 is driven to saturation by Qi . Regenera-
tion will take place if [I + (R 2/Ri )] [R4 (R3 + R4)] > I. 
As C2 begins to charge, the base voltage of Qi de-
creases exponentially until Q2 comes out of satura-
tion. Negative regeneration then occurs and the circuit 
AM	 (continued overleaf) 
MF
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=19660000178 2020-03-11T17:30:39+00:00Z
turns off. The base voltage required to remove Q2 
from saturation is approximately the supply voltage 
divided by the forward gain [Ecc/(l + R2/R 1 )]. In 
effect, a negative resistance of magnitude [—R 1 R3/R2] 
appears in parallel with the input impedance seen 
at the base of Q. If the resultant impedance is nega-
tive, switching takes place. 
The output pulse width may be varied by changing 
the forward gain [I + R 2 /R 1 ]. The width may 
be changed by a factor of ten or more by varying R2. 
Temperature compensation is obtained by inserting 
the proper thermistor in series with R1. 
Notes: 
I. By placing a zener diode across R2 , the effects of 
power supply and beta variations are made negli-
gible. The operation is the same as described above 
until the voltage across R 2 reaches the zener 
voltage, E. At this time the forward gain is unity 
and regeneration ceases. Both Q and Q2 are then 
operating on the linear portion of their charac-
teristic curves, provided the supply voltage is 
greater than E, (I + R4 /R 3 ). The input impedance 
is now 02 R 1 . When the zener diode conducts, the 
voltage across R3 and C2 remains constant. The 
current through R4 is essentially the current
through R3 and C2, and is decreasing exponenti-
ally. When the current through R 1
 decreases to 
where the zener can no longer conduct, negative re-
generation takes place and the circuit turns off. 
2. This circuit exhibits high rejection of spurious 
triggers, is easy to design, is capable of pulse widths 
of 0.5 microsecond, is easily temperature com-
pensated, and has an easily controlled output 
width. It is, however, limited to low duty cycles. 
The addition of the zener diode makes the output 
pulse width independent of beta. 
3. Inquiries concerning this invention may be di-
rected to:
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland, 20771 
Reference: B66-10179 
Patent status: 
Inquiries about obtaining rights for the commer-
cial use of this invention may be made to NASA, Code 
GP, Washington, D.C., 20546. 
Source: Leonard L. Kleinberg and

Richard C. Lavigne 
(GSFC-433) 
Brief 66-10179	 Category 01


Complementary monostable circuits achieve low power drain and high reliability

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