SELECTIVE AMPLIFIER Russian patent published in 2013 - IPC H03F3/00 

FIELD: radio engineering, communication.

SUBSTANCE: selective amplifier has a first input transistor, the base of which is connected to a signal source and the emitter is connected to a first power supply bus, a second input transistor, the emitter of which is connected to the first power supply bus and the collector is connected to a second power supply bus, a first balancing capacitor connected between the emitters of the first and second input transistors. The first balancing capacitor is connected in series to a first frequency-setting resistor; between the base of the second input transistor and the first power supply bus there is a second frequency-setting resistor, a second balancing capacitor, connected through alternating current in parallel to a second frequency-setting resistor, an additional transistor, the collector of which is connected to the output of the device and the base of the second input transistor, the base is connected to an additional voltage source, and the emitter is connected to the second power supply bus. The collector of the first input transistor is connected to the input of an additional current mirror, the collector output of which is connected to the first power supply bus, and the common emitter output is connected to the emitter of the additional transistor.

EFFECT: high Q-factor of the amplitude-frequency curve of the amplifier and its voltage gain at quasi-resonance frequency.

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