Tom=E1s =D3 h=C9ilidhe wrote: > * You put 5 V on the input > * Current flows into the base resistor, into the base, across the B-E > junction dropping 700 mV in the process, No. Look up "darlington" transistor configuration and you will see it is really two transistors. ******************************************************************** Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products (978) 742-9014. Gold level PIC consultants since 2000. -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist