FUNCTIONAL BLOCK DIAGRAMS

GENERAL DESCRIPTION

The SSM2018T and SSM2118T represent continuing evolu-

tion of the Frey Operational Voltage Controlled Element

(OVCE) topology that permits flexibility in the design of high

performance volume control systems. Voltage (SSM2018T)

and differential current (SSM2118T) output versions are of-

fered, both laser-trimmed for gain core symmetry and offset. As

a result, the SSM2018T is the first professional audio quality

VCA to offer trimless operation. The SSM2118T is ideal for

low noise summing in large VCA based systems.

Due to careful gain core layout, the SSM2018T/SSM2118T

combine the low noise of Class AB topologies with the low dis-

tortion of Class A circuits to offer an unprecedented level of

sonic transparency. Additional features include differential in-

puts, a 140 dB gain range, and a high impedance control port.

The SSM2018T provides an internal current-to-voltage con-

verter; thus no external active components are required. The

SSM2118T has fully differential current outputs that permit

high noise-immunity summing of multiple channels.

Both devices are offered in 16-pin plastic DIP and SOIC pack-

ages and guaranteed for operation over the extended industrial

temperature range of –40

°C to +85°C.

*Protected by U.S. Patent Nos. 4,471,320 and 4,560,947.

FEATURES

117 dB Dynamic Range

0.006% Typical THD+N (@ 1 kHz, Unity Gain)

140 dB Gain Range

No External Trimming Required

Differential Inputs

Complementary Gain Outputs

Buffered Control Port

I–V Converter On-Chip (SSM2018T)

Differential Current Outputs (SSM2118T)

Low External Parts Count

Low Cost

Trimless

Voltage Controlled Amplifiers

SSM2018T/SSM2118T*

Information furnished by Analog Devices is believed to be accurate and

reliable. However, no responsibility is assumed by Analog Devices for its

use, nor for any infringements of patents or other rights of third parties

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106,

U.S.A. Tel: 617/329-4700

Fax: 617/326-8703

REV. A

a

–IN

+IN

GAIN

CORE

G

1–G

SSM-2018T

–IN

+IN

GAIN

CORE

G

1–G

SSM-2118T