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2-2-1-2.
Read c i r c u i t
The read c i r c u i t c o n s i s t s of head m a t r i x s w i t c h , p r e - a m p l i f i e r , low
p a s s f i l t e r , d i f f e r e n t i a t i o n a m p l i f i e r , peak d e t e c t o r , S i - d i r e c t i o n a l
edge d e t e c t o r , o u t p u t d r i v e r , e t c .
Main c i r c u i t s a r e enclosed i n t h e
read w r i t e LSI,
U2.
The minute v o l t a g e induced i n read o p e r a t i o n by t h e r e a d / w r i t e head i s
i n p u t t o p r e - a m p l i f i e r v i a m a t r i x switch f o r s e l e c t i n g s i d e
0/1
heads.
The p r e - a m p l i f i e r has t h r e e g a i n s e t t i n g t e r m i n a l s ,
G S O ,
G S 1
and GSC.
In
B
and
F
models,
GSO-GSC
i s s h o r t e d t o o b t a i n t h e g a i n of 1 1 5 t i m e s ,
approx., while GS1-GSC
i s
s h o r t e d i n
G
model t o o b t a i n t h e g a i n of
230
t i m e s , approx.
The pre-amp.
o u t p u t i s s u p p l i e d t o t h e d i f f e r e n t i a t i o n a m p l i f i e r v i a
t h e low p a s s f i l t e r and t h e switch f i l t e r t o e l i m i n a t e u n d e s i r a b l e
high frequency n o i s e s .
The d i f f e r e n t i a t i o n a m p l i f i e r p h a s e - s h i f t s t h e
peak p o s i t i o n of t h e reproduced waveform t o z e r o c r o s s p o i n t , and a t
t h e same
t i m e ,
f u r t h e r a m p l i f i e s t h e s i g n a l with t h e m o s t a p p r o p r i a t e
e q u a l i z a t i o n .
The d i f f e r e n t i a t e d o u t p u t s a r e s u p p l i e d t o t h e peak
d e t e c t o r c o n s t r u c t e d with a comparator a f t e r p a s s i n g through t h e
coupling c a p a c i t o r s , C20 and
C 2 1 ,
and converted i n t o a square wave.
Then t h e edges of t h e square wave a r e d e t e c t e d by t h e b i - d i r e c t i o n a l
edge d e t e c t o r and they a r e o u t p u t a s t h e read d a t a p a u l s e s from t h e
F D D through t h e
RD
d r i v e r and t h e
RD/INDEX
g a t e i n t h e c o n t r o l LSI, U1.
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211
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