Type A Chopper or First–Quadrant Chopper This type of chopper is shown in the figure. It is known as first-quadrant chopper or type A chopper. When the chopper is on, v0 = VS as a result and the current flows in the direction of the load. But when the chopper is off v0   is zero but I0  continues to flow in the same direction through the freewheeling diode FD, thus average value of voltage and current  say V0  and I0  will be always positive as shown in the graph.