Current-switching pulse stretcher overcomes the diode nonlinearity and capacitive feedthrough of voltage switching diode-capacitor stretchers and lengthens nanosecond pulses so that their amplitude may be determined and extends the dynamic range of the pulse stretcher. The rise time of the output pulse in response to a step function is approximately 5 nanoseconds

Larsen, R. N.

English

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November 1966	 Brief 66-10509 
.1,	 AEC-NASA TECH BRIEF 
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. 
Pulse Stretcher Has Improved Dynamic Range and Linearity 
—25V
The problem: 
To lengthen nanosecond pulses so that their ampli-
tude may be determined and to extend the dynamic 
range of the pulse stretcher. The most serious limita-
tion of the commonly used diode—capacitor stretcher 
is the nonlinear attenuation of the diode for signals 
of less than a few hundred millivolts. Also, when 
operating in the nanosecond range the diode capaci-
tance allows partial feedthrough of the signal to pro-
duce distortion. 
The solution: 
A current-switching pulse stretcher to overcome the 
diode nonlinearity and capacitive feedthrough of volt-
age switching diode—capacitor stretchers. 
How it's done: 
The figure shows the complete circuit of the current 
switching nanosecond pulse stretcher. When no input 
is present, the quiescent operating conditions are such 
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
that 02 and 03 are biased into the active region. The 
quiescent current in 02 is adjusted with P 1 so that D1 
conducts approximately 10 microamperes. Since D1 
draws little current, the emitter potential of 04 is 
nearly zero and 04 is held in cutoff. 
An input pulse enters through the base of emitter 
follower 01. 01 drives the differentiating capacitor 
C1 . A current proportional to the derivative of the 
input voltage passes through 02 to the diode switching 
circuit, D 1
 and 04. The signal current switches D1 
off and turns 04 on. The output from the collector 
Of 04 rapidly charges C2 . As the differentiated pulse 
returns to zero, 04 turns off, leaving a charge on C1. 
When 04 is turned off, C2 discharges exponentially 
through R1 , with a time constant of approximately 
R1 C2 . R1
 is selected to give the desired decay time 
of the stretched pulse. The input impedance of emitter 
followers 05 and Qr, is high compared to R 1 and there-
fore isolates C2
 from the output load.
(continued overleaf) 
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=19660000507 2020-03-11T17:37:37+00:00Z
The voltage swing at the emitter of Q4 is small so 
that the effect of capacitive feedthrough from emitter 
to collector of Q4 during the trailing edge of the input 
is negligible. There is a slight threshold in the circuit 
due to the 10-microampere quiescent current in D1, 
as well as the charge which is lost in charging the 
stray capacitance across D 1 . This effect is made quite 
small by choosing C1 large enough so that the full 
scale current pulse is large compared to 10 micro-
amperes. 
Notes: 
1. The rise time of the output pulse in response to a 
step function is approximately 5 nanoseconds. 
2. The differential linearity of the output is 1-2 per-
cent over an output range of 50 millivolts to 10 
volts. 
3. Additional information is contained in Rev. Sci. 
Instr., vol. 37, no. 4, p. 514-515, April 1966.
4. Inquiries concerning this innovation may be di-
rected to:
Office of Industrial Cooperation 
Argonne National Laboratory 
9700 S. Cass Avenue 
Argonne, Illinois 60439 
Reference: B66-10509 
Patent status: 
Inquiries about obtaining rights for commercial use 
of this innovation may be made to: 
Mr. George H. Lee, Chief 
Chicago Patent Group 
U.S. Atomic Energy Commission 
Chicago Operations Office 
9800 S. Cass Avenue 
Argonne, Illinois 60439 
Source: R. N. Larsen
Electronics Division
(ARG-82)
. 
Brief 66-10509	 Category 01


Pulse stretcher has improved dynamic range and linearity

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