Patent ID: 8489030
Filing Date: 2013-07-16
Classification: H03F,H03G

Abstract:
1. A radio apparatus having an input terminal, comprising: a first amplifier to amplify a signal inputted to the input terminal with an amplification gain determined by a variable resistor to generate a first amplified signal; a first correcting unit to correct a direct current offset of the first amplifier; a second amplifier to amplify the first amplified signal to generate a second amplified signal; a second correcting unit to correct a direct current offset of the second amplifier; a reference voltage source or reference current source to supply a reference voltage or reference current for referring a direct current offset to the first amplifier and the second amplifier; a first switch to connect an input of the first amplifier to one of (i) the input terminal and (ii) either the reference voltage source or the reference current source; a second switch to connect an input of the second amplifier to one of (i) an output of the first amplifier and (ii) either the reference voltage source or the reference current source; a gain controller to control the amplification gain of the first amplifier; and a correction controller to (i) control the second switch to connect the input of the second amplifier to the reference voltage source or the reference current source so as to perform correction of the second correcting unit based on the second amplified signal obtained by supplying the reference voltage or the reference current to the input of the second amplifier, and thereafter, (ii) control the second switch to connect the input of the second amplifier to the output of the first amplifier and control the first switch to connect the input of the first amplifier to the reference voltage source or the reference current source so as to perform correction of the first correcting unit based on the second amplified signal obtained by supplying the reference voltage or the reference current to the input of the first amplifier while the amplification gain is set to maximum by the gain controller.