Size and thickness of field adjusting plate can be varied. Memory chip specification is relaxed, since chips in structure need not be matched in bias margin

Chen, T. T.

English

NASA Technical Reports Server

October 1975	 B75-10221 
NASA TECH BRIEF 
Langley Research Center	
- 4'r 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Variable-Gap Bias Structure for
Magnetic Bubble Memory Package 
A permanent magnet bias structure has been 
designed which can accommodate bubble memory 
chips with different bias requirements. The basic 
design of the bias structure is conventional, but the 
size and thickness of the field adjusting plate can be 
varied to match the different bias requirements of 
memory chips inside the bias structure. Because the 
chips in the bias structure need not be matched in the 
bias margin, the memory chip specification is relaxed; 
and therefore the processing yield is increased. It is 
possible for a large bias structure to be used, which 
simplifies the design and reduces the module size and 
weight. 
In the conventional design, the single bias structure 
requires that all chips be closely matched in the bias 
margin. This requirement greatly limits the tolerance 
in garnet wafer and device processing. Rather than 
mass producing a large number of chips to be sorted 
out into matched groups, it would be advantageous to 
design a bias structure to accommodate chips with 
different bias requirements. This type of structure is 
shown in. the illustration.
Field 
Top Bias	 Adjusting 
	
Plate	 Plate 
	
I	 I
A staircase-type plate is used as the bias plate 
instead of a flat one. If the bias plate has sufficiently 
low coercivity, so that the magnetic potential drop 
across the plate is negligible, then the magnetic field 
H under the plate is a function of the gap width 1 
according to the following relationships: 
HJlgØ=H1 lg1 =H2lg = .	 .	 (1) 
H0
 : H1 : H2 : 
= l/lgØ: 1119 : 'lg: . . .	 (2) 
or /H 1 /H0 = (H 1 - H0)/H0 = (lg - 
=Ll1/lg1	 (3) 
Therefore, the local field inside the bias structure 
can be adjusted by varying the gap width according to 
equation 3. This thickness variation can be achieved 
by simply epoxy bonding the magnetic plate (such as 
Mumetal or ferrite plate) to the basic bias plate. The 
regular method of adjusting the bias field by using 
magnetic shunt is still applicable to the present 
arrangement and will not change the relative field 
value in the bias structure. 
- 
4flM H0
I go 1
It
Ig1 1
If
H2 t g2 
4
I
H3
1g3	 . 1 I _ 4
Magnet	 \ Bottom Bias
	 Magnet' 
Plate 
Variable-Gap Bias Structure for Magnetic Module 
With Different Biased Memory Chips
(continued overleaf) 
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 Slates 	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19750000221 2020-03-19T20:29:55+00:00Z
Note: Patent status: 
No further documentation is available. Specific
	 Title to this invention has been waived under the 
questions, however, may be directed to:
	 provisions of the National Aeronautics and Space Act 
Technology Utilization Officer	 [42 U.S.C. 2457(0], to the Rockwell International 
Langley Research Center 	 Corporation, 3370 Miraloma Avenue, Anaheim, 
Mail Stop 139-A	 California 92803. 
Hampton, Virginia 23665 
Reference: B75-10221
	 Source: Thomas T. Chen of

Rockwell International Corp. 
(LAR-1 1765) 
Categories: 01 (Electronics - Components 
and Circuitry) 
B75-10221	 03 (Physical Sciences)


Variable-gap bias structure for magnetic bubble memory package

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server