| 摘要 |
A high gain RF amplifier comprises first and second common-emitter transistor amplifier stages coupled in cascade between an RF input terminal to which RF signals to be amplified are applied and an RF output terminal from which amplified RF signals are derived. A first RF signal feedback path is coupled between the emitter of the second common-emitter transistor amplifier stage and the RF input terminal. A directional coupler is connected to provide a second, high reverse isolation RF signal feedback path between the output terminal and the emitter of the first common-emitter transistor amplifier stage. The first RF signal feedback path preferably comprises a resistor-capacitor circuit coupled in series between the emitter of the second common-emitter transistor amplifier stage and the base of the first common-emitter transistor amplifier stage. The directional coupler comprises a four port ferrite directional coupler having a first port coupled to the collector of the second common emitter transistor amplifier stage, a second port coupled to the output terminal, a third port coupled to the emitter of the first common emitter transistor amplifier stage and a fourth port coupled to a reference impedance termination.
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