An Automated External Defibrillator (AED) for delivering therapeutic electrical energy to a patient's heart comprising at least one variable capacitance capacitor having a large positive voltage coefficient such that a given amount of energy can be stored at a lower voltage than a traditional fixed capacitor having an equivalent capacitance. Due to the variable capacitance capacitor's ability to store energy at a lower voltage, initial defibrillation current levels are reduced effectively minimizing the risk of tissue damage caused by high initial current levels. In addition, the use of a variable capacitance capacitor reduces the amount of current decay throughout the discharge cycle as opposed to current AED designs utilizing fixed capacitance capacitors which experience an exponential decline in defibrillation current during the discharge cycle.