| 摘要 |
The A/D converter converting an analog input signal into a digital output signal is constructed with a band pass DeltaSigma modulator. The band pass DeltaSigma modulator includes: a resonator showing a band-pass characteristic at a predetermined frequency and an attenuation characteristic at another frequency; a quantizer; and a local D/A converter. A signal of difference between the analog input signal and a local analog signal of the local D/A converter is supplied to the resonator. The A/D converter further includes an adder for supplying the analog input signal to an input of the quantizer. In addition, signal transmission circuits for reducing the influence of spike noise of the quantizer on the input to the resonator are connected between an input of the adder and an input of resonator selectively. The A/D converter constructed with the band pass DeltaSigma modulator is improved in S/N ratio.
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