Wide PRIME-current range for all-magnetic shift registers

In an all-magnetic resistance-type shift register, a PRIME current pulse
i_{p}(t)
, of amplitude I
p
, is applied to N
p
and N
b
turns through the minor and major apertures, respectively. For given operation frequency
f
, the ratio
R = I_{p}^{max}/I_{p}^{min}
, where
I_{p}^{min} < I_{p} < I_{p}^{max}
is the PRIME range of bistable operation, is maximized by matching
N_{p}/N_{b}
so that
I_{p}^{max}
values determined by spurious ZERO buildup and ONE dropout are the same. For a rectangular (or dc)
i_{p}(t)
, the matched
N_{p}/N_{b}
is fixed by the core properties, and R
^max
is limited (e.g., <7). However, if
i_{p}(t)
rises gradually, the matched
N_{p}/N_{b}
depends also on the rise time T
r
of
i_{p}(t)
. The lower
f
is, with corresponding larger T
r
, the smaller is the matched
N_{p}/N_{b}
, and the larger is R
^max
. Calculation of
R
is carried for ramp and half-sinusoidal
i_{p}(t)
waveforms. The latter, for instance, at
T = 25\deg
C yields R
^max
values of 14.0 and 22.0 for
f
of 1.0 and 0.5 kc/s respectively. Such wide PRIME ranges permit reliable register operation in a wide temperature range without resorting to temperature compensation of I
p
. Experimental results are in agreement with the calculation.