In many measurement applications, it is required to have digital-to-analog converters (DAC). All DACs use a reconstruction (anti-imaging) filter as the final step in the conversion process. Without this filter, generating a continuous-amplitude signal would not be possible. This paper presents a new theoretical concept of a post-DAC continuous-time filter. The proposed filter was designed so as to provide both a constant group delay over the desired frequency band and a maximally flat magnitude response. Moreover, the filter coefficients were varied in the time in order to accelerate the filter response. Results verifying the effectiveness of the proposed approach are presented and compared to the performance of a traditional lowpass reconstruction filter.