Patent ID: 6052026
Filing Date: 2000-04-18
Classification: H03G

Abstract:
A linear gain-controlled amplifier powered by a current supply having AC and DC components, comprising:a differential transistor pair comprising a first transistor and a second transistor, each transistor having an emitter, a collector and a base, said collectors being coupled in series with respective first and second load resistors to a first terminal of said current supply, said emitters being coupled together and to a second terminal of said current supply;first and second amplifiers having corresponding first and second inputs coupled to the collectors of the first and second transistors respectively and having corresponding first and second amplified output terminals;first and second low-pass filters having input terminals coupled to the first and second output terminals respectively and having corresponding first and second DC output terminals;a first error amplifier having first and second input terminals coupled to the first DC output terminal and a control signal respectively and having an error output terminal coupled to the base of said second transistor; anda second error amplifier having first and second input terminals coupled to the second DC output terminal and the control signal respectively and having an error output terminal coupled to the base of said first transistor.