Lowimpedance

Low impedance refers to a relatively small opposition to alternating current in a circuit or component. Impedance is the combination of resistance and reactance that a circuit presents to AC signals, and a low-impedance source or path means this opposition is small in magnitude over the frequencies of interest. A low-impedance source can deliver more current with less voltage drop across itself, helping to keep the output signal stable when the load changes.

In practical terms, low impedance is valued for several reasons. It improves voltage regulation under varying load, reduces the influence of stray resistance and cable losses, and increases the ability to drive reactive or demanding loads without a large drop in signal level. It also enhances damping and transient response when driving loudspeakers and other power loads, and it tends to improve noise immunity by minimizing the effect of external perturbations on the signal.

Applications of low impedance occur across electronics. Audio amplifiers and line drivers are commonly designed with low output impedance to reliably drive cables and loudspeakers. In contrast, many signal sources and measurement devices emphasize high input impedance to avoid loading the source. Designers must consider frequency dependence, as impedance can vary with frequency, and ensure stability when driving capacitive or reactive loads, where very low impedance at one frequency may interact with circuit dynamics.

See also: impedance, damping factor, impedance matching, source impedance.