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.
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