In this paper, we discuss an optimization-based approach for design space exploration to find limitations and possible trade-offs between performance metrics in analog circuits. The exploration guides the designer when making design decisions. For the design space exploration, which is expensive in terms of computation time, we use an optimization-based device sizing tool that runs concurrent optimization tasks on a network of workstations. The tool enables efficient and accurate exploration of the available design space. As a design example, we investigate three operational transconductance amplifiers, OTAs, implemented in a standard 0.35-mum CMOS process. This example shows that large savings in terms of chip area and power consumption can be made by selecting the most suitable circuit.