Vitaliy wrote: >> > > On page 5, it looks like D3 is missing ground connection? No, they are using only the top two diodes of D3. The circuit in the lower left corner is being powered by a full wave bridge, but the top two diodes come from D3 and the bottom two from D1. Note the connection going down just to the right of the bottom of D1. That way the ground of the Q4-Q6 circuit is more closely tied to that of the main circuit, with the only difference being which side of the balun. Using the same part for D3 was apparently more convenient than two separate diodes or a different part with only two diodes in it. ******************************************************************** 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