Calibration method, a/d converter, and radio device

A calibration method for an A/D converter including a first amplifier to amplify first and second voltage signals, a second amplifier to amplify the first and second voltage signals amplified by the first amplifier, a first comparator to compare the first and second voltage signals amplified by the second amplifier, a third amplifier to amplify third and fourth voltage signals, a fourth amplifier to amplify the third and fourth voltage signals amplified by the third amplifier, a second comparator to compare the third and fourth voltage signals amplified by the fourth amplifier, a first generation unit to generate an intermediate voltage signal between the first and third voltage signals amplified by the first and third amplifiers, respectively, a second generation unit to generate an intermediate voltage signal between the second and fourth voltage signals amplified by the first and third amplifiers, respectively, a fifth amplifier to amplify the intermediate voltage signals generated by the first and second generation units, respectively, and a third comparator to compare the intermediate voltage signals amplified by the fifth amplifier, the method comprising:

• short-circuiting input ports of each of the second and fourth amplifiers;
• comparing the first and second voltage signals inputted to the first comparator;
• comparing the third and fourth voltage signals inputted to the second comparator;
• comparing the intermediate voltage signals inputted to the third comparator;
• calibrating output voltages of the second, fourth and fifth amplifiers in accordance with results of the comparisons by the first to third comparators, respectively;
• short-circuiting input ports of each of the first and third amplifiers;
• opening the short-circuited input ports of each of the second and fourth amplifiers;
• comparing the first and second voltage signals inputted to the first comparator;
• comparing the third and fourth voltage signals inputted to the second comparator;
• and
• calibrating output voltages of the first and third amplifiers in accordance with results of the comparisons by the first and second comparators, respectively.

An A/D converter comprising:

• a first amplifier to amplify first and second voltage signals;
• a second amplifier to amplify the first and second voltage signals amplified by the first amplifier;
• a first comparator to compare the first and second voltage signals amplified by the second amplifier;
• a first switch to short-circuit input ports of the first amplifier;
• a second switch to short-circuit input ports of the second amplifier;
• a first calibration unit to calibrate output voltages of the second amplifier in accordance with a result of the comparison by the first comparator while the second switch is keeping on;
• and
• a second calibration unit to calibrate output voltages of the first amplifier in accordance with the result of the comparison by the first comparator while the first switch is keeping on and the second switch is keeping off.

A radio device comprising:

• a receiver to receive a radio signal;
• a converter to convert the radio signal into a baseband signal including first and second voltage signals;
• a first amplifier to amplify the first and second voltage signals converted by the converter;
• a second amplifier to amplify the first and second voltage signals amplified by the first amplifier;
• a comparator to compare the first and second voltage signals amplified by the second amplifier thereby to generate a digital signal;
• a first switch to short-circuit input ports of the first amplifier;
• a second switch to short-circuit input ports of the second amplifier;
• a first calibration unit to calibrate output voltages of the second amplifier in accordance with a result of the comparison by the comparator while the second switch is keeping on;
• a second calibration unit to calibrate output voltages of the first amplifier in accordance with the result of the comparison by the comparator while the first switch is keeping on and the second switch is keeping off;
• and
• a signal processor to demodulate the digital signal from the first comparator.