Full Wave Rectifier

The full wave rectifier passes BOTH the positive and negative half cycles of the AC input through the load, in the same direction, so it is called a full wave rectifier. Its centre-tap circuit uses a centre-tapped transformer, two p-n junction diodes $D_1$ and $D_2$, and a single load resistor $R_L$; the centre tap G is usually grounded as the zero-voltage reference, so each diode only ever rectifies HALF of the total secondary voltage. During the POSITIVE half cycle, terminal M is positive, G is at zero, and N is negative -- this forward biases $D_1$ (which conducts, sending current along path $M\to D_1\to A\to G\to C$) while reverse biasing $D_2$ (which stays off), so the positive half-cycle voltage appears across $R_L$ in the direction G to C. During the NEGATIVE half cycle, terminal N is positive, G is at zero, and M is negative -- this reverses the roles, forward-biasing $D_2$ (current flows $N\to D_2\to B\to G\to C$) while reverse-biasing $D_1$, so the negative half-cycle voltage ALSO appears across $R_L$ in the SAME direction, G to C. Because both halves of the AC input are rectified and pushed through the load in the same direction, the output -- though still pulsating -- never drops to zero the way the half wave rectifier's does, and the full wave rectifier's efficiency is exactly TWICE the half wave rectifier's, 81.2%. …