DCförvrängning

DCförvrängning is a type of signal distortion that introduces a non‑zero average value, or DC component, into a waveform that is expected to have a zero mean. The term is used in electrical and electronic engineering to describe the deviation of an ideal alternating‑current (AC) signal after it has passed through a system that is not perfectly balanced or that contains components with offset errors.

When a signal is distorted by DCförvrängning, the entire waveform is shifted vertically. In audio circuits this can cause the speaker to vibrate at a constant bias level, potentially damaging it. In radio‑frequency and data transmission circuits the added DC can drive active devices out of their linear region, cause clipping, and reduce overall signal fidelity. The presence of a DC component can also bias subsequent stages, making analogue-to-digital conversion less accurate and increasing noise.

Common causes of DCförvrängning include mismatched coupling capacitors, thermal drift of transistors, soldering errors that introduce unintended series resistances, and offsets in operational amplifiers. It can also arise from unbalanced power‑supply rails or from the improper use of bias tees in RF circuits.

Measurement of DCförvrängning is typically performed by low‑pass filtering the output and recording the mean voltage, or by using a voltmeter on the output of the final stage. The level of distortion is compared to the expected zero baseline to quantify the error.

Mitigation techniques involve using high‑quality, low‑leakage capacitors for coupling, careful component matching, adding high‑pass filters at appropriate stages, and selecting op‑amps with low offset voltage. In audio applications placing a DC‑blocking capacitor between the output and the speaker eliminates the constant offset. In precision instrumentation, guarding against ripple and temperature drift in power supplies is essential to keep DCförvrängning within acceptable limits.