| 摘要 |
PURPOSE:To attain ease of monolithic circuit integration by making switching frequencies different and driving an equivalent resistor so that the product between the ratio of a maximum capacitance to the minimum capacitance of a capacitor in a filter and the ratio of switching frequencies driving switch elements for a switched capacitor equivalent resistor is constant. CONSTITUTION:The switched capacitor equivalent resistor 1 is switched by a clock phi1 and an inverted clock phi1' in a frequency f1 and similarly, the equivalent resistors 2, 3 are switched respectively by phi2, phi3 and phi2', phi3' in frequencies f2, f3. An output of an operational amplifier (OPI), that is, a transfer coefficient with the constitution above is expressed in equation I and the angular frequency omega0 is expressed in equation II. Further, the selectivity Q and the gain coefficient H of the characteristic constant are a function of switched frequencies as expressed in equations III, IV. Then in obtaining the desired Q, H, the capacitor ratio is decided to be a prescribed value and the switching frequency is decided to make the product between the capacitor ratio (CR1/CR2) and the frequency ratio (f1/f2) is made constant.
|
