Tunnel-diode circuit starts clipping action as input voltage crosses zero axis. This clipper circuit is effective as limiter in FM receiver

Bush, E. G.

English

NASA Technical Reports Server

3V	
0	 Input 
B  01	 [ 
oj-tc 
T0 T 1
 T2 T3 
.8V 
le 4 
Input
January 1965	 Brief 65-10002 
NASA TECH BRIEF 
-it 
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. 
Tunnel-Diode Circuit Features Zero-Level Clipping 
A1
state. Both diodes are biased at their peak-point volt-
ages. As the negative-input voltage moves towards 
positive, the current through diode 1 increases until at 
T 1
 the peak-current value is reached and diode I 
switches to the high-voltage state. The rapid decrease 
in current through diode 1 causes a back emf to ap-
pear across the inductor. The negative pulse appearing 
at point A, due to the voltage developed across the in-
ductor, causes diode 2 to switch to its low-voltage/ 
high-current state and the output voltage at point C 
falls to the zero level. As the positive voltage (peak 
at T2 ) decreases, the current through diode 2 will in-
crease until, at T3
 which is at exactly input voltage 
zero, the peak current value of diode 2 is reached and 
it switches to the high-voltage/low-current state. At 
.	
(continued overleaf) 
This document was prepared under the sponsorship of the National 	 this document, or that the use of any information, apparatus, method, 
Aeronautics and Space Administration. Neither the United States Govern- 	 or process disclosed in this document may not infringe privately-owned 
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes
	 rights; or B. Assumes any liabilities with respect to the use of, or for 
any warranty or representation, express or implied, with respect to the
	 damages resulting from the use of, any information, apparatus, method, 
accuracy, completeness, or usefulness of the information contained in	 or process disclosed in this document. 
The problem: Clipper circuits are used in a wide 
variety of applications. Often, clipping action must 
start as the input voltage crosses the waveform zero 
axis (positive-to-negative or negative-to-positive tran-
sition point). Conventional transistor and diode cir-
cuits have been designed for this function but generally 
fail to maintain the start of clipping at the zero point. 
The solution: A tunnel-diode circuit that provides 
clipping action as the voltage crosses the zero axis. 
Separate outputs are provided for positive and nega-
tive clipping. 
How it's done: At time T0
 the input voltage is 
negative, diode I is in the low-voltage/high-current 
state and diode 2 is in the high-voltage/low-current
https://ntrs.nasa.gov/search.jsp?R=19650000002 2020-03-11T17:16:47+00:00Z
this time, T 3 , the inductive voltage at A is positive and 
diode 1 switches to the low-voltage/high-current state. 
In this manner, diode I and diode 2 will switch to the 
opposite voltage/current state at every zero crossing 
(times T 1 and T 3 ) of the input voltage. Switching time 
is in the order of nanoseconds. The positive square 
waves which appear at B and the negative square 
waves which appear at C will rise and fall exactly co-
incident with the respective zero crossing of the input 
voltage regardless of the frequency, amplitude, or 
shape of the input signal, within the limits of circuit 
operation. Resistors R and R 2 and diodes 3 and 4 
provide the biasing and compensating 'circuits for the 
tunnel diodes. Resistors R 3 and R4 are the load re-
sistors for outputs B and C respectively. 
Notes: 
1. This circuit would be effective as a limiter in any 
FM receiver.
2. The circuit has been operated successfully over a 
wide frequency range and at temperatures from 
_50o to +70°C. 
3. Inquiries concerning this invention may be directed 
to:
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland, 20771 
Reference: B65-10002 
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: Edgar G. Bush 
(GSFC-241) 
Brief 65-10002	 Category No. 01


Tunnel-diode circuit features zero-level clipping

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