PURPOSE: To miniaturize a switched capacitor filter and reduce the price by incorporating a control circuit with a memory function in a semiconductor substrate forming a basic filter block.
CONSTITUTION: On a semiconductor substrate, a general basic filter block which has the variable constant of a transfer function is formed and control circuit CNT with a memory function is incorporated in the substrate. According to desired filter characteristics, constants α1, α2, β1 and β2 are determined and a capacitor to be selected is determined correspondingly. Connection/disconnection data of this capacitor are stored in the memory part of control circuit CNT. Next, the contents of the memory are read out, the selected capacitor is connected, and constants α1 to β2 are set to desired values, thereby setting desired filter characteristics. Thus, integrated circuits can be mass-produced, and consequently while its price is reduced, the number of pins is also reduced, so that it can be miniaturized.
KATOU SEIJI
UENO NORIO
