Complex sentence: Parasitic capacitance and parasitic inductance of component leads and PCB traces may create unwanted feedback paths between the output and input of the active device, creating instability and oscillations at unwanted frequencies.
Split into simpler sentences: Parasitic capacitance and parasitic inductance of component leads and PCB traces become significant. These may create unwanted feedback paths between the output and input of the active device, creating instability and oscillations at unwanted frequencies.