A 2.5 V, 30 MHz-100 MHz, 7th-order, equiripple group-delay continuous-time filter and variable-gain amplifier implemented in 0.25 /spl mu/m CMOS

The block-diagram of the filter and variable-gain amplifier (VGA) and their respective specs. are shown. For high-frequency applications, the two options commonly used for integrating these filters are (1) Gm-C and (2) Gm-Opamp-C structures. The Gm-C topology suffers from low DC gain and, more importantly, high sensitivity to parasitic capacitance at the output node. The Gm-Opamp-C structure chosen here, does not suffer from the forementioned problems and is modified to further improve its high-frequency characteristics.