We consider theoretically the lasing properties of distributed-feedback master-oscillator poweramplifiers which are compact semiconductor laser devices capable of emitting a high brilliance beam at an optical power of several Watts. Based on a traveling wave equation model we calculate emitted optical power and spectral maps for increasing current injections of the power amplifier. We show that a proper choice of the coupling coefficient of the Bragg grating allows to optimize the laser operation, so that the laser emits a high intensity continuous wave beam without previously observed mode jumps or dynamic instabilities when injection currents are tuned.