A global sliding-mode controller can ensure sliding behaviour throughout an entire response for applications of a motor drive. The desired specifications, disturbances and uncertainties of parameters are considered in the design, and the range of allowable reference input (RARI) is then estimated under the constraint on control activities and the sliding mode requirement; conversely, the designers can specify the demands on the capability of a servo driver to achieve a desired performance. To verify the proposed scheme, we performed experiments on its implementation in a DC brushless servo system. The advantages of the proposed scheme were indicated by comparison with the conventional sliding-mode scheme; the coherence of the theoretical estimates and the experimental results were tabulated for further validation of the proposed scheme.