A logarithmic potentiometer, often referred to as a "log pot," is a type of variable resistor commonly used in electronic circuits and audio applications. It is a three-terminal device that allows you to adjust the resistance across its terminals by turning a shaft. The resistance between two of the terminals remains constant, while the third terminal (the wiper) is connected to the adjustable contact that moves along the resistor track.
The key characteristic of a logarithmic potentiometer is that the resistance varies logarithmically with the angle of rotation of the shaft, rather than linearly as in a regular potentiometer (linear pot). This means that the change in resistance for each degree of rotation is not constant but instead increases or decreases proportionally to the logarithm of the rotation angle.
The logarithmic potentiometer is commonly used in audio-related applications, such as volume controls or tone controls in audio amplifiers and other audio equipment. The logarithmic taper matches the way human ears perceive loudness changes, making it more suitable for volume control. As we perceive loudness on a logarithmic scale (e.g., doubling the power output doesn't double the perceived loudness), using a log pot allows for a more natural and smooth volume adjustment.
There are two main types of logarithmic potentiometers: audio taper (logarithmic A) and reverse audio taper (logarithmic C). The audio taper is the most common, and its resistance increases exponentially as the shaft is turned clockwise. The reverse audio taper, as the name implies, is the opposite and has a resistance that decreases exponentially with clockwise rotation.
When you see potentiometers labeled with values like "A10k" or "C100k," the letter (A or C) indicates the taper type, and the number (e.g., 10k or 100k) denotes the potentiometer's total resistance in ohms.
Overall, logarithmic potentiometers are essential components in various electronic circuits, particularly in audio-related applications, where smooth and accurate volume control is desired to match human perception.