A combined battery charger and motor driver circuit assembly includes a plurality of power transistors arranged as a planar array, a cold plate configured to couple heat from each of the transistors in the array, a conductive power coupling fitting (also termed a bus bar), at least one capacitor, and a ferrite bead filter surrounding a necked section of the bus bar. The bus bar has a plurality of individually electrically conductive layers, each two of the layers being separated by an insulating layer, each conductive layer providing a plurality of contacts, the contacts in a layer configured to provide electrical contact, in the alternative, for power transistor collectors or power transistor emitters. The laminated bus bar is extended to form a fishtail shape along a specified section distal to the power transistors. The fish tail section terminates in two electrical contacts configured to provide electrical contact via discrete conductors to respective positive and negative battery terminals. A top surface of the capacitor is conductive at least in part. The capacitor makes electrical and thermal contact with a conductor of the laminated bus bar distal to the transistor array. A bottom surface of the capacitor is also conductive at least in part and is in electrical contact with a conductor of the laminated bus bar proximal to the transistor array.