DACs

Digital-to-analog converters (DACs) are electronic devices that convert digital numbers, typically encoded in binary, into analog voltages or currents. They are essential in systems that require a real-valued signal derived from digital processing, such as audio playback, telecommunications, instrumentation, and control systems. Most DACs take a digital word and produce an output that is proportional to the full-scale reference voltage or current, with accuracy determined by design and components.

Operation and interfaces: DACs accept parallel or serial digital inputs, often with a fixed reference voltage that defines full-scale output. The output is commonly a voltage that can be buffered by an op-amp or a current that is converted to voltage externally. Performance is described by resolution (bits), bandwidth or sampling rate, and accuracy metrics such as integral nonlinearity (INL), differential nonlinearity (DNL), signal-to-noise ratio (SNR), and total harmonic distortion (THD).

Architectures: Binary-weighted resistor ladders and R-2R ladder networks provide a monotone, staircase-like output. Sigma-delta DACs use oversampling and noise shaping to achieve high resolution at audio rates. Other approaches include segmented, current-output, and multiplying DACs. Output stages may be voltage or current, with an op-amp buffer and often an analog filter to smooth the reconstruction.

Applications and considerations: DACs drive speakers and headphones in audio gear, convert digital video or sensor data to analog signals in instrumentation, test equipment, and control systems. Important design considerations include monotonicity (to avoid non-monotonic steps), glitch energy during code transitions, reference and power supply stability, temperature drift, and clock jitter in sampling DACs. Interfaces include SPI, I2C, or parallel lines; some high-speed devices use standards such as JESD204B.

In summary, DACs translate digital information into real-world signals, enabling digital processing to control analog actuators, audio transducers, and measurement equipment.