To improve accuracy of an A/D converter by a voltage to frequency conversion method.
The A/D converter includes a voltage to frequency conversion circuit having a voltage controlled oscillator 24 with two equivalent saw tooth wave generating circuits 18A, 18B and a switching circuit 19 for alternately switching two saw tooth wave generating circuits 18A, 18B. Preferably, the A/D converter includes a first voltage controlled oscillator for outputting a first period cyclical signal and second voltage controlled oscillator for outputting a second period cyclical signal that not only is different from the first period but also keeps a predetermined ratio with the first period. Further, the A/D converter, calculates high order bits of a digital signal corresponding to an input analog signal based on the first cyclical signal included in a sampling period and then low order bits of the digital signal based on the number of waves of the cyclical signal to be included during the period from when the sampling signal is activated until the time when the phases of the first and second cyclical signals are coincided.
KAKEHI TATSUYA
JPS5118459A | 1976-02-14 | |||
JPS51105755A | 1976-09-18 | |||
JPS4711768B1 | ||||
JPS4949847U | 1974-05-01 | |||
JP2006333203A | 2006-12-07 |
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