Capacitive physical quantity detector

A capacitive physical quantity detector comprising:

• a capacitance unit having an electrostatic capacitance, which is changeable according to physical quantity;
• a converting unit for converting a electrostatic capacitance change to a voltage;
• and
• a selecting unit,
• wherein the converting unit includes a C-V converting circuit, which has an operational amplifier for amplifying an first output signal from the capacitance unit, a main switch disposed between an input terminal and an output terminal of the operational amplifier, a plurality of feedback capacitors and a plurality of feedback switches,
• wherein each feedback switch is connected in series with a corresponding feedback capacitor,
• wherein each feedback switch connects a corresponding feedback capacitor in parallel to the main switch when the feedback switch is closed,
• wherein the selecting unit selects at least one of the feedback switches based on an second output signal of the converting unit so that the one of the feedback switches is closed,
• wherein the selecting unit includes a comparator and a switching element,
• wherein the comparator compares a voltage of the second output signal from the converting unit with a predetermined threshold voltage, and
• wherein the switching element switches the feedback switches according to an third output signal from the comparator so as to set a voltage of the second output signal of the converting unit smaller than a saturated voltage of the second output signal of the converting unit and larger than the threshold voltage.