A potentiometer is used to adjust the overall level of electricity passing through a device. Normally utilized in items such as volume control knobs and light dimmers, standard analog potentiometers allow an individual to modulate the responsiveness of a circuit, controlling the flow of power therein. A digital potentiometer, or digipot, is entirely controlled via digital signals; during use, these signals are converted into an analog output, allowing the user to control the electrical signal. Digital potentiometers are typically used for modulating analog signals in microcontrollers, such as central processing units in a computer. By controlling the amount of power passing through microcontrollers, the potentiometer acts to keep the power flowing through sensitive electronic devices under tight control.
Digital potentiometers are built using either a R-2R resistor ladder integrated circuits or using a direct digital-to-analog converter. In either case, these devices take the digital binary code generated by the digital potentiometer and translate it into an analog voltage signal for the device. This results in the proper amount of power moving to the device, allowing modulations to be made through nothing more than adjustments to the digital signal moving through the device.
When compared to traditional potentiometers, digital potentiometers have some shortcomings. The first of these is modulation; digital signals cannot be adjusted quite as minutely as analog signals, resulting in adjustments that cannot be made quite as precisely. Most common are 256 step digital potentiometers, but ones ranging from 32 to over 1,000 steps are also available. Another drawback is the limitation to their digital supply range of voltage, which typically moves from 0 to 5 volts of direct current (VDC), less than the standard range of most analog potentiometers. Occasionally, during a power-on cycle, a digital potentiometer can default to a random value, which can potentially cause problems on the circuit.
Some versions of a digital potentiometer contain onboard memory. This allows them to remember their specific setting even after the flow of power moving through the device has been interrupted, such as from a user turning off a computer or other electric device. For these types of digital potentiometers, as soon as they are turned back on, they immediately resume operating at the exact power level they were at prior to shutdown.