UTC571
LI
NEAR I
NTEGRATED CI
RCUI
T
G
R1
20K
R1
10K
C
REC
T
C
F
R
D
C
R
DC
C
IN
V
IN
R3
20K
V
OUT
R4
30K
V
REF
Figure 4. Basic Components
Figure 4 shows the hook-up for a compressor. This is essentially an expandor placed in the feedback loop of the
op amp . the
∆G
cell is setup to provide AC feedback only, so a separate DC feedback loop is provide by the two
R
DC
and C
DC
. The values of R
DC
will determine the DC bias at the output of the amp. The output will bias to:
V
OUT
DC
=
1
+
R
DC1
+
R
DC2
R
4
)1.8V
30K
V
REF
=
(1
+
R
DCTOT
The output of the expander will bias up to:
V
OUT
DC
=
1
+
R
3
R
4
)1.8V
=
3.0V
V
REF
V
REF
=
(1
+
20K
30K
The output will bias to 3.0V when the internal resistor are used. External resistor may be placed in series with r3,
(which will affect the gain ), or in parallel with r4 to raise the DC bias to any desired value.
YOUW ANG ELECTRONI CO.
CS
LTD
7
UTC-IC [ UNISONIC TECHNOLOGIES ]
