SSM-2122 Просмотр технического описания (PDF) - Analog Devices

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SSM-2122

Dynamic Range Processors/Dual VCA

Analog Devices 

SSM2120/SSM2122

In the noise gate, downward expander and compressor/limiter

applications, this potentiometer will establish the onset of the

control action. The sensitivity of the control action depends on

the value of RT.

For a positive unipolar control output add two diodes as shown

in Figure 7a. This is useful in compressor/limiter applications.

Figure 7b shows a typical response.

Bipolar control outputs can be realized by adding a resistor from

the op amp output to V+. This is useful in compandor circuits

as shown in Figure 8a, with its response in Figure 8b. The value

of the resistor RPV will determine the maximum output from the

control amplifier.

STEREO COMPRESSOR/LIMITER

The two control circuits of Figures 6 and 7 can be used in

conjunction to produce composite control voltages. Figures 9a

and 9b show this type of circuit and transfer function for a

stereo compressor/limiter which also acts as a downward

expander for noise gating. The output noise in the absence of a

RIN

L

RIN

MONO

OR R

REC IN

2V

MONO – RIN = 10kΩ

STEREO – RIN = 20kΩ

THRESHOLD V+

CONTROL

|IIN|

VT

V+

RT

39kΩ

1kΩ

RPV RCON

CON

OUT

TO –VC

200Ω

LOG AV

THRESH

CAV

1.5MΩ

V–

THRESHOLD

+

*

–

*UPPER LIMIT CAN BE FIXED BY

VALUE OF PULL UP RESISTOR (RPV)

CONNECTED TO POSITIVE SUPPLY

V–

VIN – dB

a. Control Circuit

b. Typical Compressor/Limiter Control

Curve

Figure 7. Compressor/Limiter Control Circuit and Typical Response

RIN

L

RIN

MONO

OR R

RECIN

RLL

2V

MONO – RIN = 10kΩ

STEREO – RIN = 20kΩ

V+

GAIN

|IIN|

V+ V–

VT

RT

RPV

39kΩ

1kΩ

CONOUT

LOG AV

THRESH

CAV

1.5MΩ

V–

V–

TO +VC

OR –VC

200Ω

*

+

VT < 0 VT = 0 VT > 0

–

*UPPER AND

LOWER LIMITS CAN

BE ESTABLISHED BY

* VALUES OF RPV AND

RLL, RESPECTIVELY

VIN – dB

a. Control Circuit

b. Typical Compandor Control Curves

Figure 8. Compandor Control Circuit and Typical Curves

THRESHOLD EXP.

EXPANSION

THRESHOLD

COMPRESSION

THRESHOLD

L

MONO

OR R

FIGURE 6

+VC

200Ω

THRESHOLD COM.

FIGURE 7

–VC

200Ω

*

VIN – dB

a. Control Circuit

b. Input/Output Curve

Figure 9. Control Circuit for Stereo Compressor/Limiter with Noise Gating and Input/Output Curve

–6–

REV. C

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