Circuit arrangement for switching a mobile radio transmitter between two modulation modes

Disclosed is a circuit arrangement for regulating operation of a transmitter of a mobile communication terminal, which runs in the EDGE and GMSK modulation modes. The inventive circuit arrangement comprises:-a power amplifier ( 13 ) supplying an output signal for an antenna ( 17 ) of the mobile communication terminal;-a phase regulator that is provided with a phase comparator ( 11 ) to which a setpoint signal for the output signal of the power amplifier ( 13 )is fed, and a voltage-controlled oscillator ( 15 ) adjusting the phase position of the output signal of the power amplifier ( 13 ), said phase regulator regulating the phase position of the output signal of the power amplifier (13);-an amplitude-regulating device that is provided with an amplitude comparator ( 12 ) to which the setpoint signal for the output signal of the power amplifier ( 13 ) is fed, and a battery-powered battery-voltage modulator ( 16 ) adjusting the amplitude of the output signal of the power amplifier, said amplitude-regulating device regulating the amplitude of the output signal of the power amplifier ( 13 ); and-a feedback line feeding an actual measured value for the output signal of the power amplifier ( 13 ) back to the phase comparator ( 11 ) and the amplitude comparator ( 12 ), said feedback line being provided with an adjustable amplifier ( 14 ) which is controlled by a baseband chip and sets an output power of the antenna. The aim of the invention is to make the circuit arrangement for the two modulation modes EDGE and GMSK more economic. Said aim is achieved by providing the inventive circuit arrangement with a changeover switch (S 1 ) which is wired in such a way that said changeover switch (S 1 ) connects an input of the battery-voltage modulator ( 16 ) to an output of the amplitude comparator ( 12 ) in a first position for the EDGE mode while connecting an input of the battery-voltage modulator ( 16 ) to an output of the power amplifier ( 13 ) in a second position for the GMSK mode, the connection being made via the adjustable amplifier ( 14 ) in both positions.