Fuel cells are emerging as primary power source for portable applications. The output voltage from a fuel cell suffers from a 2 to 1 variation from no load to full load. Furthermore, staking fewer cells in series results in a less complex fuel cell stack. In view of this a boost type dc-dc converter becomes necessary for powering the electronics. The purpose of this paper is to explore design considerations for a fuel cell powered dc-dc converter for portable applications. First, methods to determine electrical equivalent circuit for small portable fuel cells is discussed. The equivalent circuit is then employed to evaluate the system transient response for load changes and determine the effects of continues and discontinues conduction operation of the dc-dc converter on the fuel cell performance. Finally, experimental results on 20W and SOW PEM fuel cell powered dc-dc converters are presented.