Type E or the fourth quadrant chopper consists of four semiconductor switches and four diodes arranged in antiparallel.  The 4 choppers are numbered according to which quadrant they belong. Their operation will be in each quadrant and the corresponding chopper only be active in  its quadrant.
	
First Quadrant
During the first quadrant operation the chopper CH4 will be on . Chopper CH3 will be off and CH1 will be operated.  AS the CH1 and CH4 is on the load voltage v0 will be equal to the source voltage Vs  and the load current i0  will begin to flow . v0 and i0 will be positive as the first quadrant operation is taking place. As soon as the chopper CH1 is turned off, the positive current freewheels through CH4  and the diode D2 .  The type E chopper acts as a step- down chopper in the first quadrant.
	
Second Quadrant
In this case the chopper CH2 will be operational and the other three are kept off. As  CH2 is on  negative current will starts flowing through the inductor L . CH2 ,E and D4.  Energy is stored in the inductor L as the chopper CH2 is on. When CH2 is off the current will be fed back to the source through the diodes D1 and D4. Here (E+L.di/dt) will be more than the source voltage Vs  . In second quadrant the chopper will act as a step-up chopper as the power is fed back from load to source
	
Third Quadrant
In third quadrant operation CH1 will be kept off , CH2 will be  on and CH3 is operated. For this quadrant working the polarity of the load should be reversed. As the chopper CH3 is on, the load gets connected to the source  Vs and  v0 and i0 will be negative  and the third quadrant operation will takes place. This chopper acts as a step-down chopper
	
Fourth Quadrant
CH4 will be operated and CH1, CH2 and CH3 will be off. When the chopper CH4 is turned on positive current starts to flow through CH4, D2 ,E and the inductor L will store energy. As the CH4 is turned off the current is feedback to the source through the diodes D2 and D3 , the operation will be in fourth quadrant as the load voltage is negative but the load current is positive. The chopper acts as a step up chopper as the power is fed back from load to source