A circuit is provided for regulating operation of a transmitter of a mobile communication terminal, which runs in the EDGE and GMSK modulation modes. The inventive circuit includes a power amplifier supplying an output signal for an antenna of the mobile communication terminal; a phase regulator that is provided with a phase comparator to which a setpoint signal for the output signal of the power amplifier is fed, and a voltage-controlled oscillator adjusting the phase position of the output signal of the power amplifier, the phase regulator regulating the phase position of the output signal of the power amplifier; an amplitude-regulating device that is provided with an amplitude comparator to which the setpoint signal for the output signal of the power amplifier is fed, and a battery-powered battery-voltage modulator adjusting the amplitude of the output signal of the power amplifier, the amplitude-regulating device regulating the amplitude of the output signal of the power amplifier; and a feedback line feeding an actual measured value for the output signal of the power amplifier back to the phase comparator and the amplitude comparator, the feedback line being provided with an adjustable amplifier which is controlled by a baseband chip and sets an output power of the antenna. The inventive circuit includes a changeover switch which is wired in such a way that it connects an input of the battery-voltage modulator to an output of the amplitude comparator in a first position for the EDGE mode while connecting an input of the battery-voltage modulator to an output of the power amplifier in a second position for the GMSK mode, the connection being made via the adjustable amplifier in both positions.