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The product ks k2 can be conveniently determined
for the actual transducer from the following
approximate relationship
Table 1 presents a few results obtained by this
method on different types of material and with
different designs of the transducer, in all cases at
optimum biasing.
An entirely closed magnetic circuit as shown in fig.
2 was not employed, but in certain specified cases
the transducer was fitted with end plates of
magnetically soft ferrite. The most favourable material
according to the table is nickel-cobalt from The
Mond Nickel Company, Great Britain. The supplier
states its optimum k value to be 0.59, which
indicates that the most favourable’ ks value in this case
would be 0.21. Judging from the data for k, it seems
that more favourable values of ks, of the order of
0.5, have been attained with magnetostrictive ferrite
rods. This is only to be expected since eddy current
losses in the metallic line materials also contribute
to decrease the value of k<y
For other questions concerning magnetostrictive
delay lines, such as attenuation, frequency distor-
tion and phase distortion, and the temperature
dependence of the propagation coefficient on the
mechanical line, reference is made to the literature,
especially [2].
As a general assessment it may be said that, for
normal memory purposes in data processing,
magnetostrictive delay lines — even of optimum design
— can only compete with ferrite memories in
exceptional cases since the output signals are of the same
order of magnitude as those from ferrite memories
at equal driving currents. In addition,
magnetostrictive delay lines have such specific disadvantages as
high delay/temperature coefficient, high sensitivity
to mechanical influences, and fairly high
self-induc-tance in transmitter and receiver coils.
References
1. Bradburd K M: Magnetostrictive Delay Line. Electrical
Communication, March 1951, pp. 46—53.
2. Scarrott G (1, Naylor R: Wire-Type Acoustic Delay Line for
Digital Storage. PIEE Paper No. 2027 M, March 1956, PIEE, Vol.
103, Part B Suppl. No. 1, pp. 497—508.
3. Van der Burgt C M: Ferro.vcube Material for Piezomagnetic
Vibrators. Philips Technical Review, Vol. 18, 1956—57, No. 10 pp.
285—316.
4. Rothbart A, Rosenberg L: A Theory of Pulse Transmission
along a Magnetostrictive Delay Line. IRE Transactions on
Ultrasonics Engineering PGUE-6, Dec. 1957, pp. 32—58.
On the Temperature Margins of a Transistor-Driven
Coincident Current Ferrite Core Memory
Jan-Rustan Törnquist, SAAB, Linköping
För ett tänkt transistordrivet tvåkoincidensminne
med ferritkärnor beräknas drivströmsmarginalerna.
En ny kärnkarakteristik, lämpad för
marginalbedömning av minnet presenteras. Med hjälp härav kan
utföras beräkningar av temperaturintervall,
erforderliga drivspänningar och maximal minnesstorlek
liksom en bedömning av olika drivningsalternativ.
In a transistorized ferrite core coincident current
memory for digital computers the temperature
margins for accurate performance depend on the
drive circuits and their properties as well as on the
ferrite cores themselves. The purpose of this paper
is to discuss this matter and to give a method for
calculating the recommended temperature interval
of high reliable performance of a given memory
system in terms of the ferrite core drive current
characteristics. The method has proved to be
suitable for marginal calculation in general.
A coincident current ferrite core memory
To get a background to this discussion let us assume
a hypothetic transistor-driven coincident current
memory as in figs. 1 and 2.
From the amplifiers current pulses are fed to the
matrices and pass the rows and columns being
621.318.042 : 621.314.7
addressed by the transistors Tx and Ty. As a first
approach the row and column current pulses are
determined by the drive voltage sources Ebi or
Eb^ and the resistances R.s in fig. 2. Any variation in
the drive voltage and the series resistance thus gives
variations in the drive current pulse amplitude. A
detailed analysis will demonstrate several more
factors contributing to the drive current tolerances.
Calculation of drive-current amplitudes
and tolerances
The row drive current, Ix, during the read phase
can be calculated from fit?. 3.
K =
E-Vt- I • R -VT- v
b ^ ij Is lx b
Rs + Rui
(i)
Ix — row current, E^ = drive voltage
// = sum of leakage currents of all reversed
selection switch transistors
V — saturation voltage of T1
Ji
V — saturation voltage of Tx
1 X
Rs — series resistance, Rw = wire resistance
v = back voltage in selected drive wire due to
switched cores and wire inductance, vij = vi, (t)
ELTEKNIK 1959 1 95
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