Actually, I've seen FETs fail shorted and stay shorted up to a very high current level! On Thu, Aug 30, 2012 at 4:40 PM, Spehro Pefhany wrote: > At 04:11 PM 30/08/2012, you wrote: >>On 31 August 2012 05:02, Paul Anderson wrote: >> > There are 110 volt LED bulb replacements, but they are pretty expensiv= e. >> >>One could easily enough [tm] build an LED driving from mains supply >>that provided power to a reservoir capacitor when Vmains is under say >>10V near the zero crossing points. There are power supply ICs that do >>that, but it should be possible to do a minimalist version with 2 >>transistors * and a few Rs Cs and Ds. * - A FET as main pass element >>as bipolar as gate clamp maybe. FET gate is whispered on by mains but >>clamped off by bipolar when mains is above target max. feed with 1/2 >>wave or full wave as desired. >> >>May need a bit more glue to ensure it ALWAYS fails FET off when there >>is any doubt :-). > > There is no doubt in my mind that it would always fail off-- just > in some cases there may be a bit more smoke than others. > > --sp > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .