Abstract: A digital tank circuit, having a center frequency f.sub.0, which includes a circuit that samples an analog input signal at a predetermined sampling interval and converts the sampled signal into a binary code as well as a digital filter that is responsive to the binary code and has a gain characteristic with a sharp peak at the center frequency. The digital filter is implemented without multipliers to provide a transfer function given by ##EQU1## where (l) is an integer and (n) is the number of bits in the code representing each sample. Provision also is made to cancel rounding off errors generated on the filter.