Patent ID: 6246282
Filing Date: 2001-06-12
Classification: H03F,H03G

Abstract:
A first stage amplifier circuit comprising:amplifier means for amplifying an input signal supplied thereto;a variable feedback resistance means connected between an output terminal and an input terminal of the amplifier means, including two or more feedback resistors and one or more switches for changing a connection of the feedback resistors and thereby changing a composite resistance of the feedback resistors;a judgment means for judging whether the output signal of the amplifier means exceeds a first predetermined threshold value and a second predetermined threshold value; anda feedback resistance control means for operating the one or more switches of the variable feedback resistance means one by one and successively reducing the composite resistance of the feedback resistors of the variable feedback resistance means as long as the output signal of the amplifier means is judged by the judgment means to exceed the first and second predetermined threshold values.