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Maxim > Design Support > Technical Documents > Application Notes > Digital Potentiometers > APP 3996
Keywords: Digital, potentiometer, digipot, volume, control, audio, attenuation, log-taper, logarithmic,
resistance, linear, taper,
APPLICATION NOTE 3996
Logging the Linear Digital Potentiometer
Mar 08, 2007
Abstract: Digital potentiometers (digital pots or digipots) are commonly used in volume-control
applications. For audio applications, volume attenuation should closely mimic human hearing by applying
a logarithmic scale. In some designs, a simple, low-cost linear potentiometer can be used in place of a
logarithmic-taper potentiometer (log pot). This application note details how to implement a linear
potentiometer in a log-taper application using a small, low-cost, higher resolution digipot.
Download: GUI Software (ZIP, 229kB)
Introduction
Because of their resiliency, small size, and ease of use, digital potentiometers have become widely
accepted as replacements for mechanical potentiometers, particularly in volume-control applications. In
this type of audio application, it is often preferable to use a log-taper pot instead of a linear-taper pot
because the human ear perceives the logarithmic attenuation of sound as linear attenuation. However, as
this application note demonstrates, a high-resolution linear potentiometer can also be used to implement
volume control. The following analysis shows how to use a linear digital pot as a log pot (Figure 1).
Figure 1. This family of digital pots is configured in a standard manner, as they include a connection to
both the high end and the low end of the resistor string, as well as a wiper connection that moves
among the resistor string's tap points.
Using a Linear Digipot as a Log Pot
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