BASF 6106 - Page 35

READ/WRITE
SELECT
The
read/write
select
circuit
comprises
two
MOS-
FET
switches.
The
inputs
of the
switches
are
connected
to
the
read/write
coils
of the
read
write
head.
The
output
of
the
switches
are
connected
to
the
read
preamplifier
(see
Fig.
2
-
3o
)•
When
the
disk
drive
is
operating
in
the
WRITE-
ode,
WRTENA;01
is
high
and T6
and T7
are
open.
The
read/write
coils
are
isolated
from
the
read
preamplifier.
In
the
Read-
mode
(WRTENA;01
-*
low)
the
output
signal
of
the
selected
read
write
head is
switched
to
the
read
preamplifier.
READ
AMPLIFIERS
AND
FILTER
NETWORK
(Fig.
2
-
37
)
For
amplification
of
the read signal a
high
gain
linear
amplifier
of
the read
LSI and
an
external
transistor
stage are used. Both
circuits
increase
the
read signal amplitude
by a
gain
of
—
•
300.
This
amplified
signal
is
used to drive
a fil-
ter
network.
The
filter
network
is
alow
pass
l'iltci
with a
bandwith
of
—
400
kHz.
FROM
THE
WRITE
i
likiXITS
&
>
—
w-
P/J.
READ/
WRITE
HEAD
5
1
R68
'24V
fh
u'kte?;a;oi
Tb
S
D
©5"
TO
THE
—
)
I
READ
C -L
r-
PREAMPLI-
FIER
©Si
S
D
T7
F I
GURU 2
-
36 . READ/
WRITE
SELECT LOGIC
FIGURE
2
-
57
.
READ
AMPLIFIERS
AND FILTER
NETWORK
2-25