Patent ID: 7956638

Claim:
An impedance adjusting circuit comprising: an external terminal to which an external resistor is connected; a first transistor array of a first conductivity type that is connected between the external terminal and a first power supply terminal and changes a voltage of the external terminal by adjusting an impedance in response to a first control signal; a second transistor array of a second conductivity type that is connected between the external terminal and a second power supply terminal and changes the voltage of the external terminal by adjusting the impedance in response to a second control signal; a control unit that specifies the first control signal according to a comparison result between the voltage of the external terminal and a reference voltage and specifies the second control signal in a different period from a period to specify the first control signal; and a reference voltage generation circuit that generates the reference voltage, wherein the reference voltage generation circuit uses a first potential as the reference voltage in the period to specify the first control signal and uses a second potential as the reference voltage in the period to specify the second control signal, the reference voltage generation circuit further comprises a first resistor, a second resistor, a third resistor, and a fourth resistor that are connected in series between the first power supply terminal and the second power supply terminal, the first potential is generated according to a resistance ratio between the first resistor and the second resistor, and the second potential is generated according to a resistance ratio between the third resistor and the fourth resistor.