Which statement best describes a DAC?

• A. It generates PWM signals from digital codes
• B. It converts analog signals to digital codes
• C. It stores energy in a capacitor
• D. It converts digital values to continuous voltages

Answer: (D)

A digital-to-analog converter takes a digital word and turns it into an analog voltage or current that corresponds to that word. The key idea is that the input is discrete (a finite set of digital codes) but the output is a continuous-valued signal, so the device provides a bridge from digital representations to real-world analog levels. In practice, as the digital input changes, the output steps through levels; with proper filtering, that stepped output can be made to appear smooth as an analog waveform.

This is different from an analog-to-digital converter, which goes the other way—sampling an analog signal and producing a digital code. It’s also not simply about storing energy in a capacitor; while internal DAC circuitry may use capacitors, the purpose is to perform a conversion, not to store energy. And while PWM can be used to approximate an analog level by adjusting duty cycle, a PWM method is not the same as a true DAC, which directly maps digital values to corresponding analog voltages or currents.

So the statement that a DAC converts digital values to continuous voltages captures the essential role of a digital-to-analog converter.