Precision Monolithics Inc. reserves the right to make changes leading to improved performance, reliability or manufacturability. Although every effort is made to ensure accuracy of the information

contained on this data sheet, PMI assumes no responsibility for circuitry unless entirely contained within a PMI product. The premium performance of this product is achieved through an advanced

processing technology. All PMI products are guaranteed to meet or exceed published specifications. © PMI 1990

5/90, Rev. B1

0590 0299G7M PRINTED IN USA

Precision Monolithics Inc.

A Bourns Company

1500 Space Park Dr.

Santa Clara, CA

TWX 310-371-9541

TEL 800 843-1515

P.O. Box 58020

95052-8020

FAX 408 727-1550

®

®

FADER AUTOMATION

The SSM-2120 can be used in fader automation systems to serve

two channels. The inverting control port is connected through

an attenuator to the VCA control voltage source. The noninverting

control port is connected to a control circuit (such as Figure 6)

which senses the input signal level to the VCA. Above the thresh-

old voltage, which can be set quite low (for example –60dBV),

the VCA operates at its programmed gain. Below this threshold

the VCA will downward expand at a rate determined by the +V

C

control port attenuator. By keeping the release time constant in

the 10 to 25ms range, the modulation of the VCA standing noise

floor (–80dB at unity-gain), can be kept inaudibly low.

The SSM-2300 8-channel multiplexed sample-and-hold IC

makes an excellent controller for VCAs in automation systems.

Figure 16 shows the basic connection for the SSM-2122 operat-

SSM-2120/SSM-2122 DYNAMIC RANGE PROCESSOR/DUAL VCA

FIGURE 16:

SSM-2122 Basic Connection (Control Ports at 0V)

ing as a unity-gain VCA with its noninverting control ports

grounded and access to the inverting control ports. This is typi-

cal for fader automation applications. Since this device is a pin-

out option of the SSM-2120, the VCAs will behave exactly as

described earlier in the VCA section.

The SSM-2122 can also be used with two or more op amps to

implement complex voltage-controlled filter functions. Biquad and

state-variable two-pole filters offering lowpass, bandpass and

highpass outputs can be realized. Higher order filters can also

be formed by connecting two or more such stages in series.

1

2

3

413

14

15

16

512

611

7

89

200

Ω

0.1

µF

10

+15V

+

–

36k

Ω

10pF

SIG

OUT 1

1/2

TL082

V+

V–

50k

Ω*

220k

Ω

150k

Ω

SIN

IN 1

36k

Ω

V+

0.1

µF

+

–

36k

Ω

10pF

SIG

OUT 2

200

Ω

V+

V–

50k

Ω*

220k

Ω

200

Ω

1/2

TL082

SIG

IN 2

36k

Ω

SSM-2122

–15V

200

Ω

* OPTIONAL CONTROL FEEDTHROUGH TRIM

2000pF

47

Ω

2000pF

47

Ω

OBSOLETE