An embodiment of the invention relates to a circuit assembly having the following components: a power transistor with a control terminal, a first load terminal and a second load terminal, the second load terminal having a floating potential; a driver circuit configured to generate control signals for the control terminal of the power transistor, the relevant reference potential for the driver circuit being the floating potential of the second load terminal; a planar metallization layer sited on or in a substrate and comprising a constant reference potential, a shielding plane isolated from the metallization layer, sited planar on or in the substrate such that it is capacitively coupled to the metallization layer; a power supply circuit for providing a supply voltage referenced to the floating potential of the second load terminal for the driver circuit, the power supply circuit comprising, circuited between the second load terminal and the shielding plane, a first series circuit including a first capacitor and a first diode.