The paper presents the automated design of active RC and programmable filters. The approximating function is derived using Legendre orthogonal polynomial with the appropriate weights and usage of two Legendre multiplication factors at the origin and the pass–band edge frequency. Detailed analysis is done for the frequency response and sensitivity analysis of active RC filters. Optimisation is performed using symbolic manipulation of expressions inputted into computer algebra system and numeric solvers. The code is in the form of template notebook, and the user should specify the minimal number of numeric values, such as the number of second–order filter sections, the pass–band edge frequency, the reflection coefficient, and the preferred values of component values.