Genetic algorithms are used in the design and synthesis of fixed topology electronic circuits. Two types of circuits are considered, analog and digital. In the analog case, simple RC and FDNR filters are investigated. The aim for employing GA is to minimize the component spreads (which is defined as the maximum value to the minimum one) while satisfying the filter frequency specifications like cutoff frequency, order, and ripple factor. GAs are also employed in the digital circuits design. Several gate circuits are designed and synthesized to obtain the best value of (W/L)s for the transistors in the circuits. These aspect ratios minimize the required circuit total chip area while still satisfying the logic function of the circuit with minimum deviation from the ideal characteristics. The resultant gate structures have less aspect ratio than those resulting from the traditional design techniques.