A calculating circuit and a method for generating an output signal representing an output number approximating an N-th root and/or a reciprocal of an input number represented by an input signal are described. The calculating circuit includes a subtractor circuit, an integrator circuit, and a multiplier circuit. The subtractor circuit responsive to a first signal and a feedback signal and configured for generating an error signal representing a difference between the first signal and the feedback signal. The integrator circuit responsive to the error signal and configured for computing the output signal. The multiplier circuit responsive to the output signal and configured for generating a feedback signal. The method for generating the output signal includes the following iterative steps: (i) generating an error signal at a j-th iteration, (ii) integrating the error signal for obtaining the output signal, (iii) generating the feedback signal and (iv) repeating steps (i) to (iii) as required to obtain the N-th root and reciprocal with a required accuracy.