The invention specifies a circuit arrangement with a phase locked loop (1), which can be used as a mobile radio transmitter, in particular. The reference frequency for the PLL (1), which is provided by means of the source (3), is multiplied by a multiplier (10) and is down-converted to an intermediate-frequency level in a down-conversion mixer (9) using the output signal from the PLL, and is evaluated such that a modulator (13) connected to the input of the oscillator (6) can be trimmed. The inventive principle is used to advantage in two-point modulators and allows inexpensive, integratable mobile radio transmitters with good noise characteristics.