Abstract: The invention describes a novel circuit to be used in spark-ignition combustion engines. An ignition circuit according to the invention extends the voltage decay time following the initial generation of a spark across the spark plug gap. In addition, it reduces the oscillation of the voltage following any secondary negative spike. Use of the circuit increases combustion efficiency and reduces wear and tear on the spark plugs. This purpose is achieved by including a diode and a capacitor in the spark circuit; alternately, the diode may act as a capacitor when reverse biased.