| 摘要 |
An A/D converter comprising conversion means (51) for converting an analog voltage to an analog current, current means (54) for producing a plurality of weighted values of currents, combining means (56) for selectively combining the weighted values of currents, detection means (52, 55, 63, 68) for detecting difference in current value between the analog current and the combined current by the combining means (56), a differential amplifier (CMP) having a pair of inputs (SUM, BIAS), one (SUM) of which is supplied with a signal corresponding to the detected difference value, said detection means (52, 55, 63, 68) comprise first and second current mirror circuits (52, 55) input means (53, Q17, R10) responsive to said analog signal for applying an analog current having a value proportional to said analog signal to said input terminal of said first current mirror circuit (52), means (62) for connecting the output terminal of said first current mirror circuit (52) to the input terminal of said second current mirror circuit (55), and means for applying a reference signal to the output terminal of said second current mirror circuit (55). Preferably there are switch means (Q16) arranged between the pair or inputs (SUM, BIAS) of the differential amplifier (CMP), and control means (CK,59) for controlling the switch means (Q16), wherein the switch means (Q16) is periodically made conductive to delete potential difference between the pair of inputs (SUM, BIAS) through the A/D conversion operation. |
