Patent ID: 8166800

Claim:
A gas concentration detection apparatus which detects the concentration of a specific gas component by measuring a current which flows through a gas sensor and whose magnitude changes in accordance with the concentration of the specific gas component, the apparatus comprising: a detection resistor through which the current output from the gas sensor flows; differential amplification means having a first input terminal and a second input terminal electrically connected to opposite ends of the detection resistor, respectively, which differential amplification means differentially amplifies a potential difference generated across the detection resistor and outputs the amplified potential difference as a detection voltage; amplification factor setting means which sets an amplification factor at which the potential difference is amplified to one of at least two different amplification factors based on the value of the potential difference; potential equalization means which equalizes potentials of the first input terminal and the second input terminal; acquisition means which acquires a correction voltage for each of the amplification factors, the correction voltage being the detection voltage which is output from the differential amplification means when the potential equalization means equalizes the potentials of the first input terminal and the second input terminal; and concentration calculation means which corrects the detection voltage output from the differential amplification means based on the correction voltage corresponding to the amplification factor set in accordance with the detection voltage, and calculates a concentration corresponding value, which corresponds to the concentration of the specific gas component, on the basis of the corrected detection voltage.