Philips Semiconductors RF Communications Products
Product specification
Programmable analog compandor
NE/SA572
Basic Compressor
Figure 5 shows the hook-up of the circuit as a
compressor. The IC is put in the feedback
loop of the OPA A
1
. The system gain
expression is as follows:
R4
RDC1
9.1k
CDC
10µF
C2
.1µF
RDC2
9.1k
V
OUT
+
V
IN
I
1
R
2
@
R
1
@
2
R
3
@
V
IN
(
AVG
)
1
2
(7)
V
IN
C
IN1
–
2.2µF
R3
17.3k
+
C1
1k R5
(6,10) V
REF
R1
6.8k
A1
D1
D2
R
DC1
, R
DC2
, and CDC form a DC feedback
for A
1
. The output DC level of A
1
is given by
V
OUT
V
ODC
+
V
REF
1
)
*
R
DC
1
)
R
DC
2
R
4
(8)
V
B
@
R
DC
1
)
R
DC
2
R
4
(5,11)
(2,14)
∆G
(7,9)
C
IN2
2.2µF
The zener diodes D
1
and D
2
are used for
channel overload protection.
Basic Compandor System
The above basic compressor and expandor
can be applied to systems such as tape/disc
noise reduction, digital audio, bucket brigade
delay lines. Additional system design
techniques such as bandlimiting, band
splitting, pre-emphasis, de-emphasis and
equalization are easy to incorporate. The IC
is a versatile functional block to achieve a
high performance audio system. Figure 6
shows the system level diagram for
reference.
(4,12)
BUFFER
C
IN3
2.2µF
3.3k
R2
CR
10µF
CA
1µF
(8)
V
CC
(16)
(3,13)
Figure 5. Basic Compressor Schematic
October 7, 1987
8
PHILIPS [ NXP SEMICONDUCTORS ]
