Patent ID: 8115551

Claim:
An amplifying device that amplifies an input signal of which a signal level varies to a prescribed desired level and output an output signal, the amplifying device comprising: a first amplifying unit capable of changing its gain in a stepwise manner so that an output of the first amplifying unit is changed in a stepwise manner, the first amplifying unit performing a primary gain adjustment; a second amplifying unit cascade-connected to the first amplifying unit, the second amplifying unit being capable of changing its gain in a stepwise manner so that an output of the second amplifying unit is changed in a stepwise manner, the second amplifying unit performing a compensating gain adjusting, an adjustable gain range of the second amplifying unit being narrower than the primary gain adjustment of the first amplifying unit, and the adjustable gain range of the second amplifying unit being overlapping with a part of the gain adjustment range of the first amplifying unit; and a gain controller comprising a primary gain setting logic circuit providing a first control signal set to the first amplifying unit and a compensating gain setting logic circuit providing a second control signal set to the second amplifying unit, wherein when the gain controller receives a gain setting signal, the gain controller determines whether the second amplifying unit can adjust a gain level of the output signal to a desired level based on the gain setting signal preferentially over using the first amplifying unit.