UTC571

LINEAR INTEGRATED CIRCUIT

YOUW ANG ELECTRONICS CO.LTD

7

G

R3

20K

R4

30K

C

T

R1

10K

R1

20K

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

4

DC2

DC1

OUT

R

R

R

1

DC

V

+

+

=

)1.8V

30K

R

(1

V

DCTOT

REF

+

=

The output of the expander will bias up to:

REF

4

3

OUT

V

R

R

1

DC

V

+

=

3.0V

)1.8V

30K

20K

(1

=

+

=

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.