PURPOSE: To reduce an area occupied by resistors by decreasing a combined resistance of gain setting resistors without generating a gain error due to the effect of a conduction resistance of a gain changeover switch.
CONSTITUTION: This amplifier is made up of an operational amplifier 1 whose noninverting input terminal is connected to a reference potential, an input resistor circuit 2 receiving an input signal Vi, and a gain changeover circuit 3. The input resistor circuit 2 is formed by connecting an input resistor Ri and a dummy switch Si set conductive state by a control signal Di1 at all times in series. Then the gain changeover circuit 3 is formed by parallel connection of plural feedback resistor circuits 4f1-4fn in which a gain setting resistor Rf1-Rfn and a gain changeover switch Sf1-Sfn whose conduction/nonconduction is controlled by a gain switching control signal Df1-Dfn are used as one unit respectively.
TANAKA HIROAKI
ISHIHARA HIDEAKI
SAKISHITA HARUYASU
