Patent ID: 7663443

Claim:
An active balun circuit comprising: a load circuit unit including a first load and a second load connected in parallel to a power supply terminal; a differential amplifying unit including a first amplifying unit connected to the first load of the load circuit unit, and a second amplifying unit connected to the second load of the load circuit unit and forming a differential amplifying unit together with the first amplifying unit, the differential amplifying unit differentially amplifying an input signal supplied through an input terminal, and outputting first and second output signals out-of-phase with each other through first and second output terminals, respectively; a current source connected between a ground and a common connection node of the first and second amplifying units, and maintaining a constant amount of current flowing through the differential amplifying unit; and a compensation amplifying unit amplifying the input signal supplied through the input terminal, transmitting the amplified input signal to the second amplifying unit, and rejecting common mode noise of the differential amplifying unit.