| 摘要 |
PROBLEM TO BE SOLVED: To provide a complex filter circuit that secures flat characteristics in a passband and allows the chip area and the current consumption of the circuit to be reduced. SOLUTION: A high-order complex elliptic filter circuit of third order or higher inputs two mutually 90°-out-of-phase differential signals and outputs two 90°-out-of-phase differential signals, and the high-order complex elliptic filter has at least two circuit blocks internally having capacitors which are connected to couplers (gyrator) in series. The high-order complex elliptic filter is a third order inverse Chebyshev filter having ripple characteristics such as a stopband of 40 dB. Alternatively, a coupler (gyrator) between elliptic capacitors is removed. Alternatively, the elliptic capacitors are made nearly equal to capacitors arranged in parallel to them. Alternatively, the elliptic capacitors are removed. Alternatively, a gm value and a capacity value of OTA constituting a circuit are integral ratios almost represented by geometric series of 2 respectively. COPYRIGHT: (C)2007,JPO&INPIT
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