An implantable defibrillation circuit comprising: an implantable defibrillation therapy output circuit including: a first switch configured to controllably connect a first defibrillation therapy supply node to a first defibrillation therapy output node; a second switch configured to controllably connect a second defibrillation therapy supply node to the first defibrillation therapy output node through a first rectifier; wherein the second switch is configured to inhibit the first switch from connecting the first defibrillation therapy supply node to the first defibrillation therapy output node when the second defibrillation therapy supply node is connected to the first defibrillation therapy output node through the second switch; and wherein the first defibrillation therapy output node is configured to be coupled to a first implantable electrode, characterised in that the first switch includes a control input configured to control a conductive state of the first switch; and wherein the second switch is configured to controllably connect the second defibrillation therapy supply node to the control input of the first switch. an implantable defibrillation therapy output circuit including: a first switch configured to controllably connect a first defibrillation therapy supply node to a first defibrillation therapy output node; a second switch configured to controllably connect a second defibrillation therapy supply node to the first defibrillation therapy output node through a first rectifier; wherein the second switch is configured to inhibit the first switch from connecting the first defibrillation therapy supply node to the first defibrillation therapy output node when the second defibrillation therapy supply node is connected to the first defibrillation therapy output node through the second switch; and wherein the first defibrillation therapy output node is configured to be coupled to a first implantable electrode, characterised in that the first switch includes a control input configured to control a conductive state of the first switch; and wherein the second switch is configured to controllably connect the second defibrillation therapy supply node to the control input of the first switch. a first switch configured to controllably connect a first defibrillation therapy supply node to a first defibrillation therapy output node; a second switch configured to controllably connect a second defibrillation therapy supply node to the first defibrillation therapy output node through a first rectifier; wherein the second switch is configured to inhibit the first switch from connecting the first defibrillation therapy supply node to the first defibrillation therapy output node when the second defibrillation therapy supply node is connected to the first defibrillation therapy output node through the second switch; and wherein the first defibrillation therapy output node is configured to be coupled to a first implantable electrode, characterised in that the first switch includes a control input configured to control a conductive state of the first switch; and wherein the second switch is configured to controllably connect the second defibrillation therapy supply node to the control input of the first switch.