A/D converter and A/D conversion method

摘要

The A/D converter realizes a high-rate and high-precision A/D conversion using amplifier circuits. Each amplifier circuit amplifies a difference between the voltage of an analog signal to be converted and a predetermined reference voltage. Each bank of holding circuits holds the output signals of an oscillator circuit, the levels of which signals are variable with the passage of time, when the output voltage of the associated amplifier circuit exceeds a predetermined value. The signals held in each said bank of holding circuits are output as a value representing the amplification time of the associated amplifier circuit. An operation means identifies a first amplifier circuit having a reference voltage higher than the analog signal voltage and a second amplifier circuit having a reference voltage lower than the analog signal voltage based on the values representing the amplification times, and determines a voltage, at a point interiorly dividing a difference between the reference voltages of the first and the second amplifier circuits by a ratio of the amplification time of the second amplifier circuit to the amplification time of the first amplifier circuit, as the analog signal voltage, thereby computing a digital value representing the analog signal. <IMAGE>