Abstract: An n-stage amplifier circuit includes n+1 directional couplers connected in series between the circuit input, the amplifier stages, and the circuit output. Each coupler includes first and third ports forming an inverting interface, and second and fourth ports forming a non-inverting interface, the ports being coupled through suitable windings. Feedback lines are connected between adjacent successive couplers. The interfaces of the couplers are connected such that feedback loops covering one or more contiguous successive amplifier stages provide negative feedback for the amplifier circuit.

Abstract: 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.

Abstract: Disclosed is a broad band amplifier for use as a preamplifier in TV receiving systems and in other applications where broad band amplification is desired. A ferrite directional coupler is used to negatively feed back a portion of the output of an amplifying stage to its input.