Patent ID: 6438364
Filing Date: 2002-08-20
Classification: H03F

Abstract:
A radio frequency device comprising:an input transistor comprising an input electrode from which a capacitance is seen, said input transistor being switchable between an on-mode and an off-mode, and said input electrode receiving a radio frequency signal; and a charging circuit for charging said capacitance when said input transistor is switched from said off-mode to said on-mode, said charging circuit comprising: a differential amplifier with differential inputs and a current sensing resister connected across the differential inputs to detect a quantity of current flowing across the input transistor and to cause said charging to automatically cease if said quantity has changed from a first value to a second value, said second value occurring when said capacitance is fully charged; a first current mirror for mirroring a first output current at a first output of said differential amplifier; a second current mirror for mirroring a second output current of said differential amplifier; a third current mirror that is coupled to said first and second current mirrors, said second current mirror providing a charging current upon initiation of said charging, and said third mirror fully sinking said charging current if said quantity has adopted said second value; and a charging transistor of which an input electrode receives said charging current, and an output electrode provides a current amplified charging current, said current amplified charging current charging said capacitance.