Circuit assembly comprising - a first circuit branch comprising a series connection of a piezoelectric transformer, which makes it possible to convert a supplied AC voltage into a higher or lower AC voltage and which has an input capacitance (Cp), and a first resistor, wherein the piezoelectric transformer is between a first and a second potential point (11, 12) in the first circuit branch and the first resistor is between the second and a third potential point (12, 13) in the first circuit branch, - a second circuit branch which compensates for the input capacitance (Cp) and comprises a series connection of a capacitive element (Ck) and a second resistor (Rk), wherein the capacitive element (Ck) is between a first and a second potential point (21, 22) in the second circuit branch and the second resistor (Rk) is between the second and a third potential point (22, 23) in the second circuit branch, wherein the first and second circuit branches (1, 2) are connected in parallel and the time constant of the series connection of the capacitive element (Ck) and the second resistor (Rk) in the second circuit branch is equal to or nearly equal to the time constant of the series connection of the input capacitance (Cp) and the first resistor in the first circuit branch, and - a differential amplifier having a first input which is coupled to the first circuit branch, and a second input which is coupled to the second circuit branch, wherein the second potential point in the first circuit branch is coupled to the first input, and the second potential point in the second circuit branch is coupled to the second input and wherein an output of the differential amplifier is coupled to the piezoelectric transformer via a feedback branch. - a first circuit branch comprising a series connection of a piezoelectric transformer, which makes it possible to convert a supplied AC voltage into a higher or lower AC voltage and which has an input capacitance (Cp), and a first resistor, wherein the piezoelectric transformer is between a first and a second potential point (11, 12) in the first circuit branch and the first resistor is between the second and a third potential point (12, 13) in the first circuit branch, - a second circuit branch which compensates for the input capacitance (Cp) and comprises a series connection of a capacitive element (Ck) and a second resistor (Rk), wherein the capacitive element (Ck) is between a first and a second potential point (21, 22) in the second circuit branch and the second resistor (Rk) is between the second and a third potential point (22, 23) in the second circuit branch, wherein the first and second circuit branches (1, 2) are connected in parallel and the time constant of the series connection of the capacitive element (Ck) and the second resistor (Rk) in the second circuit branch is equal to or nearly equal to the time constant of the series connection of the input capacitance (Cp) and the first resistor in the first circuit branch, and - a differential amplifier having a first input which is coupled to the first circuit branch, and a second input which is coupled to the second circuit branch, wherein the second potential point in the first circuit branch is coupled to the first input, and the second potential point in the second circuit branch is coupled to the second input and wherein an output of the differential amplifier is coupled to the piezoelectric transformer via a feedback branch.