SA575

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7

Automatic Level Control

The

typical

Automatic

Level

Control

circuit

configuration is shown in Figure 4. It can be seen that it is

quite similar to the compressor schematic except that the

input to the rectifier cell is from the input path and not from

again, as in the previous cases, if the system input and

summing amplifier at higher input levels. This circuit

provides an input dynamic range greater than 60 dB with

the output within

"0.5 dB typical. The necessary design

expressions are given by Equation 5 and Equation 6,

respectively.

(eq. 5)

3.8 k

W x 100 mA

ALC gain =

(eq. 6)

2.2

mF

10

mF

10

mF

VREF

S

1

mF

4.7

mF

ALC IN

ALC OUT

8

12

13

16

15

11

14

C COMP

22pF

C7

Figure 4. Typical ALC Configuration

10k

W

3.8k

W

10k

W

30k

W

30k

W