Patent ID: 8654991

Claim:
An inverting amplifier comprising: an operational amplifier which comprises a first input differential pair including first conduction-type MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and a second input differential pair including second conduction-type MOSFETs; an input resistor arranged such that one terminal thereof is connected to an inverting input terminal of the operational amplifier, and an input signal to be amplified is received via the other terminal thereof; a feedback resistor arranged between the inverting input terminal of the operational amplifier and an output terminal thereof, a bias voltage source configured to generate a bias voltage, and to supply the bias voltage thus generated to a non-inverting input terminal of the operational amplifier; and a control unit configured to switch the second input differential pair between an active state and an inactive state according to the bias voltage, wherein, when a voltage that corresponds to the bias voltage is lower than a predetermined threshold value, the control unit sets the second input differential pair to the active state, and when the voltage that corresponds to the bias voltage is higher than the threshold value, the control unit sets the second differential pair to the inactive state.