A device for producing a non-thermal atmospheric-pressure plasma are a method for frequency control of a piezoelectric transformer are disclosed. In an embodiment a device includes a piezoelectric transformer, an activating circuit configured to apply an AC voltage at an activating frequency to the piezoelectric transformer as an input voltage and a field probe configured to measure a field strength of an electric field produced by the piezoelectric transformer, wherein the activating circuit is configured to adapt the activating frequency based on the measurement results of the field probe such that a field strength is maximized.