DCcoupled

DC coupling, or DC coupling in electronics, refers to a signal path where successive stages are connected directly so that direct current and very low-frequency content can pass through without attenuation or blocking capacitors. This contrasts with AC coupling, which uses capacitors or transformers to block DC components and emphasize alternating current signals.

Advantages of DC coupling include an extended lower cutoff frequency, allowing true DC and near-DC signals to be reproduced, faster transient response, and simpler signal paths without coupling capacitors that can introduce phase shift and distortion. It is often favored in precision instrumentation, servo loops, and certain audio or measurement circuits where preserving the complete signal spectrum is important.

Disadvantages and design challenges arise from the need to manage DC offsets, drift, and bias currents. Any small DC error in one stage can propagate and accumulate, potentially driving amplifiers into saturation or quiescently biasing later stages incorrectly. DC stability requires careful selection of components, tight biasing, and robust power-supply regulation. In some cases, a DC servo or feedback loop is used to correct offsets over time.

Implementation considerations include ensuring compatible biasing between stages, selecting amplifiers with suitable input/output ranges, and providing stable, clean supplies. Designers may also employ DC restoration techniques or deliberate offset control to maintain proper operating points while still benefiting from full-bandwidth, low-frequency performance.

Applications span precision analog front ends, certain audio amplifiers, DAC/ADC interfaces, and feedback or servo systems where preserving DC levels is essential. See also AC coupling and DC offset concepts.