A parasitic is an unavoidable, hidden electrical characteristic introduced by the physical construction of a component or PCB layout. Traces act as tiny inductors, adjacent pads form capacitors, and wire leads add resistance. At high frequencies or fast switching speeds, these hidden values dominate circuit behavior, causing ringing, delays, or unexpected oscillations.
The simulation looks perfect, but once you add the board parasitics, the oscillator completely stalls.
Related terms
Parasitic element
An unintended component characteristic, such as stray capacitance or lead inductance, that affects circuit operation.
PCB
A laminated board holding and connecting electronic components using conductive traces.
Layout
The physical arrangement of components and traces on a chip or circuit board.