vo the first input i 1 of the switch 3343 is connected with d 6 and the second input i 2 is connected with d 6 b when i vo is in the positive half cycle the voltage of d 6 is high and that of d 6 b is low the switches 3313 and 3343 are therefore conductive and the current flows out from the first output terminal o va and flows in from the second output terminal o vb in contrast when i vo is in the negative half cycle the voltage of d 6 is low and that of d 6 b is high the switches 3323 and 3333 are therefore conductive and the current flows out from the first output terminal o vb and flows in from the second output terminal o va a circuit diagram for the current output unit 35 is shown in fig1 the first control switch 351 and the second control switch 352 of the current output unit 35 are transistors with one terminal thereof connected with a power supply v dd and another terminal thereof connected with the switched current sources 353 and 354 respectively the first control switch 351 is controlled by a control signal s 1 and the second control.