Implementing Programmable T-Networks Using Xicor Digitally Controlled Potentiometers (XDCPs)IGSF Filters
Implementing a traditional T-network using XDCPs results in a programmable T-network, and the analog function associated with the T-network becomes programmable as well. In other words, using XDCPs puts the analog function on the bus.
Filtering is a common application of T-networks. A good example of this is a second-order, low-pass Infinite Gain Single Feedback (IGSF) filter, shown below. An IGSF filter consists of an inverting amplifier whose input, A, is a T-network, and output, B, is a bridged T-network. The factor k (the Wojslaw factor) represents the wiper position of the XDCP.