| 摘要 |
Disclosed is a complex elliptic filter having an order of three or higher which receives two differential signals that differ in phase from each other by 90 degrees are applied and outputs two differential signals that differ in phase from each other by 90 degrees. The complex filter circuit has internally at least two circuit blocks that include a capacitor connected in series with a coupler (gyrator). The complex filter is a third-order inverse Chebychev filter having an equiripple stopband of 40-dB attenuation amount. Alternatively, the coupler (gyrator) between elliptic capacitors is removed. Alternatively, the elliptic capacitors are made substantially equal to the capacitor arranged in parallel therewith. Alternatively, the gm value of an OTA and the capacitance value are each in an integral ratio represented substantially by a geometric progression of 2. |
