Storage device including calibration device

A calibration device comprising:

• a first operational amplifier configured to output a first control signal for adjusting a first resistance value of a first resistor circuit by comparing a level of a first voltage of a first node and a level of a reference voltage;
• and
• a second operational amplifier configured to output a second control signal for adjusting a second resistance value of a second resistor circuit by comparing the level of the first voltage and a level of a second voltage of a second node,
• wherein the first node is between the first resistor circuit and a reference resistor, and
• wherein the second node is between the second resistor circuit and a third resistor circuit, a third resistance value of the third resistor circuit being adjusted to have the same resistance value as the first resistance value.

A storage device comprising:

• a memory device;
• and
• a controller configured to perform a calibration operation of adjusting a first resistance value of a first resistor circuit based on a first comparison result of comparing a level of a first voltage and a level of a first reference voltage and adjusting a second resistance value of a second resistor circuit based on a second comparison result of comparing the level of the first voltage and a level of a second voltage,
• wherein the level of the first voltage is determined based on the first resistance value and a first reference resistance value, and
• wherein the level of the second voltage is determined based on the first resistance value and the second resistance value.