Patent ID: 7855596

Claim:
A demodulation circuit, comprising: a modulation ratio enhancement unit to increase the modulation ratio of a current signal which is amplitude shift keying modulated with signal data; and a demodulation unit to demodulate the signal data from the current signal, of which the modulation ratio is increased by the modulation ratio enhancement unit, wherein said modulation ratio enhancement unit further comprises a current mirror to generate first, second and third mirror currents corresponding to said current signal; a first maximum value detection unit to detect the maximum value of the first mirror current; a first subtraction unit to subtract, from the second mirror current, a first subtraction current, which is a current as a result of multiplying the maximum value of the first mirror current, which is detected by the first maximum value detection unit, by a constant; a second subtraction unit to subtract the first subtraction current from the third mirror current; a second maximum value detection unit to detect the maximum value of a current after the first subtraction current is subtracted by the first subtraction unit; and a third subtraction unit to further subtract, from a current after the first subtraction current is subtracted by the second subtraction unit, a second subtraction current, which is a current as a result of multiplying the maximum value, which is detected by the second maximum value detection unit, by a constant, wherein said demodulation unit demodulates said signal data from a current after being subtracted by the third subtraction unit.