Practical applications in electrical engineering often deal with analog signals, but there are employed also digital circuits and microcontrollers. Sometimes it is easier or cheaper to improvise DA and AD converters instead of using dedicated ones. This paper is a comparative analysis of how accurate the analog signals can be generated from digital systems, like Field Programmable Gate Arrays (FPGAs) using only additional passive circuits. For this analysis, different FPGAs families were tested. Two alternatives of generating analog signals were considered in this study: PWM and R2R network. The analysis has been performed for a common frequency band, from 100 Hz to 30 kHz, using a virtual instrument for building an automated test system. At 10 kHz the PWM module obtains better THD values, reaching even 0.013% and at 30 kHz the R2R module obtains better THD values, reaching even 0.222%.