Simple frequency divider composed of relaxation oscillators uses unijunction transistors to reduce backward loading to a minimum. This circuit design is applicable in timing devices and sync generators for television systems

Fairbanks, A. F.

English

NASA Technical Reports Server

Input -. - Pulses 
+ Pulses 
April 1965	 Brief 65-10112 
NASA TECH BRIEF 
_& 
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. 
-	 -: -	 11111 IiiiI 
Unijunction Frequency Divider Is Free of Backward Loading 
+30 V 
The problem: Present unijunction frequency di-
viders have a tendency toward loading in the back-
ward direction. This causes undesirable triggering of 
preceding stages. 
The solution: A simple frequency divider using 
unijunction transistors has few elements per stage and 
reduces backward loading to a minimum. 
How it's done: Each stage in the frequency divider 
is a relaxation oscillator. The capacitor C 1 quickly 
charges through R 2 and slowly discharges through 
R 1 and R 2. The charging current through R 2 lowers 
the voltage at point A and may cause the next stage to 
lire. However, the larger value of R 3 keeps the current 
through the base of Q 1 low so that the size of the
pulse generated in R 2 is kept so low that one stage will 
not trigger a preceding stage. Thus the circuit reduces 
loading of each stage by feeding each output into a 
low impedance loop. At the same time, backward 
loading is reduced since the synchronization signal of 
each stage is picked up by a high impedance loop in 
the following stage. This high impedance loop results 
in low currents which do not create appreciable sync 
voltages in the preceding stage. 
Notes: 
I. Circuits of this design should find application in 
timing devices and in sync generators for television 
systems.
(colitiotied Os crical 
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=19650000111 2020-03-11T17:21:48+00:00Z
2. Inquiries concerning this innovation may be di- 	 Patent status: NASA encourages commercial use 
rected to:	 of this innovation. No patent action is contemplated.

Technology Utilization Officer 
Jet Propulsion Laboratory	 Source: Avard F. Fairbanks 
4800 Oak Grove Drive	 (JPL-WOO-0I0)
Pasadena, California, 91103 
Reference: B65-101 12 
Brief 65-10112	 Category No. 01


Unijunction frequency divider is free of backward loading

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server