You can use a low-cost PC sound card as an analog-function generator by controlling the PC with the program `SoundArb.` [To obtain SoundArb, download di2409setup.exe, a 1.06-Mbyte self-extracting installation program.] The program generates standard waveforms, noise, and arbitrary waveforms. The program reads arbitrary waveforms from simple ASCII text files consisting of white-space-separated numbers. You can use a program such as Mathcad to create such files.
EDN.com Some ideal op amp configurations assume that the feedback resistors exhibit perfect matching. In practice, resistor non-idealities can affect parameters such as common mode rejection ratio (CMRR), harmonic distortion and stability.