The usual schematic of a state-variable filter with two inverting integrators is well known. Curiously, the input signal is almost always connected to the minus input of U1. Figure 1 is an example ...

This application note covers the basics of Filter design. It covers a variety of filter topologies and explains the benefits. Circuit diagrams and filter transfer functions are described in the paper.

An array of electro-optical components fabricated as a silicon-based photonic IC provides narrowband passband and notch filtering above 10 GHz. How an electro-optic PIC can implement RF filtering ...