1. The problem statement, all variables and given/known data Sketch the output waveform: http://img7.imageshack.us/img7/3774/recgraph.jpg [Broken] (The coloured lines I added myself) 2. Relevant equations Nothing which applies, I think. 3. The attempt at a solution The answer has already been provided. I just have a concept question. The full rectifier circuit is active only where the input voltage is 4 or greater (marked in blue). But why 4? Is it simply the sum of the 4 diode's threshold voltages (marked in red), that is, 1+1+1+1=4? But only 2 diodes are active at a time (at each peak or valley of the input wave), right? So, why isn't it 1+1=2 instead? Or am I on the wrong track entirely?