A circuit arrangement is provided for a power supply to a transponder including an antenna resonant circuit and a downstream rectifier circuit for receiving and for rectifying an electromagnetic signal, a charging capacitor connected downstream on the output side of the rectifier circuit to provide a first supply voltage, with a tuning circuit for tuning the antenna resonant circuit to its resonance frequency, and with an auxiliary voltage source, which is designed to provide a second supply voltage, lower than the first supply voltage, for supplying the tuning circuit. A method is also provided for supplying power to a transponder with a first supply voltage, as well as a transponder having a circuit arrangement for a power supply.