A spark ignition circuit comprising a source of high voltage and a spark gap including either a diode and a capacitor connected in parallel or a diode having an inherent capacitance such that it acts as a capacitor when reverse biased between the voltage source and the spark gap. The diode may be arranged such that when an arc in deliberately induced across the spark gap, the diode conducts the arc current. The diode/capacitor combination reduces opposite polarity voltage spikes following an initial discharge and the capacitor serves to maintain a low voltage across the spark plug terminals for a longer duration.
