Most modern defibrillators are biphasic; older models monophasic Monophasic defibrillators requires larger energy levelsFor biphasic shocks:Ventricular fibrillation / ventricular tachycardia: 200 JAtrial fibrillation: 120 JFor monophasic shocks:Vfib / vtach: 360 JAtrial fibrillation: 200 J