Low Voltage Microphone Preamplifier with Variable Compression & Noise Gating
The SSM2167 is a complete and flexible solution for conditioning microphone inputs in personal electronics and computer audio systems. It is also excellent for improving vocal clarity in com-munications and public address systems. A low noise voltage controlled amplifier (VCA) provides a gain that is dynamically adjusted by a control loop to maintain a set compression characteristic. The compression ratio is set by a single resistor and can be varied from 1:1 to over 10:1 relative to the fixed rotation point. Signals above the rotation point are limited to prevent overload and to eliminate popping. A downward expander (noise gate) prevents amplification of background noise or hum. This results in optimized signal levels prior to digitization, thereby eliminating the need for additional gain or attenuation in the digital domain. The flexibility of setting the compression ratio and the time constant of the level detector, coupled with two values of rotation point, make the SSM2167 easy to integrate in a wide variety of microphone conditioning applications.
The device is available in a 10-lead MSOP package, and is guaranteed for operation over the extended industrial temperature range of −40°C to +85°C.
The AN-583 application note provides a basic explanation of how the board is set up and how to use it to evaluate the SSM2167. This document is only a supplement and makes several references to figures contained in the product data sheet. The current data sheet for the SSM2167 is available on-line.
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.