Adding to Olin's comment and Joe's question. Probably the reason that Schottky diodes are less seen in this role in higher power applications is that their special properties are not needed and they are costlier per performance. Schottky's are now seen at much higher voltages than originally, due mainly to the Silicon Carbide technology, and prices are good for what they do, but they are expensive relative to "silicon" diodes. Schottky has 'rather poor' reverse leakage currents at room temperature and 'utterly abysmal" leakage currents at say 100 C. As in the role mentioned here they are reverse biased during normal use their reverse leakage current becomes part of the on current when the switch etc is on (so not usually significant) (but bypasses the load so this current is not "useful") but when the main switch is off the leakage current predominates. As a good albeit somewhat extreme example, the IR 100BGGQ015 is rtaed at 100A and 15 V VRRM. At Tj =3D 25 C the maximum reverse leakage current is 18 mA. Hardly significant compared to 100 A. But certainly noticeable. BUT at Tj =3D 100C Irm max is 700 mA max at 12 V reverse voltage, and at 125 C it's 1.2 A at 5V reverse voltage. They don't specify it at 12 V at 125 C :-). That's "only" 1.2% of Imax but having 1.2A off current can be extremely unacceptable. As a bonus, Vf (forward voltage) drops with rising temperature at currents below 100% rating. eg about 0.25V at 10A at 25C but about hald that at 10A 125C. Fig 8 is specially for Joe - inductive clamp test at large current. Russell McMahon --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .