| 摘要 |
PROBLEM TO BE SOLVED: To reduce the number of voltage comparison frequencies required for a high resolution A/D converter having a noise elimination function. SOLUTION: A clamp means 102 clamps an input signal in a form of being superimposed on a fluctuating DC component at no signal to reset an integrator 106, and a sample-hold means 107 holds the output voltage of an adder 105 as a reference value. A step wave as a reference signal is given to a differential amplifier 104 at an input period of a signal component to activate the differential amplifier like a successive approximation AD converter and to decide a high-order digital value, and the sample-hold means 107 holds a residual voltage. The reference signal is changed by using an amplitude of the decrease of the step voltage of the step wave by a multiple of 1/2, the integrator 106 is used to apply successive approximation to the residual voltage for AD conversion, and one bit each of low order digital values is decided from the high order digital value. When the number of steps of the step waveform for deciding the high order digital value is set as K, and the number of comparison frequencies for the low order values as L, a digital value with (K×2<SP>L</SP>) gradations can be obtained by voltage comparisons for (K+L) times so that the AD converter with a high resolution at low noise can be obtained. COPYRIGHT: (C)2005,JPO&NCIPI
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