Oli Glaser wrote: >> and bipolars more like a voltage source. > > Do you mean current source here? No, I was talking about the on-state of switching applications when the BJT is saturated. The do look like a controlled current source in the linear operating mode, but that's not relevant when we're talking about switching relay coils on and off. ******************************************************************** Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products (978) 742-9014. Gold level PIC consultants since 2000. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .