Static and dynamic characteristics of MQW DFB lasers with varying ridge width are investigated theoretically with respect to various waveguide parameters. It is shown that varying the ridge width provides a convenient method to control the lasing mode, longitudinal field distribution, quantum efficiency and modulation bandwidth. Comparisons of static and dynamic behaviours among various DFB lasers with varying ridge width and conventional lambda /4-shifted DFB lasers are made for the first time. Some interesting features of these devices are pointed out and discussed in detail.