High frequency differential amplifier, differential mixer, differential oscillator and radio circuit using same

摘要

In order to enhance a reverse isolation characteristic of a differential amplifier, which is used as, for example, an RF amplifier or a local amplifier of a mobile telephone, the present invention provides a differential amplifier which includes a differential amplification circuit 10 for amplifying a difference in potential between two input signals in reverse phase with each other, which are inputted into Port1 and Port2, and for outputting two output signals in reverse phase with each other from Port3 and Port4; a feedback capacitor 7a connected between Port1 and Port4; and a feedback capacitor 7b connected between Port2 and Port3. Signals for canceling feedback signals are inputted into input terminals via the feedback capacitors 7a and 7b, respectively, whereby it is possible to the reverse isolation characteristic of the differential amplifier.