A common topology found in many analog circuits is the
T-network, so called because its schematic representation resembles
the letter “T”. T-networks are two port structures used as building
blocks in amplifiers, filters, oscillators and conversion
circuits.

Traditionally, T-networks networks have been constructed using
discrete resistors and capacitors. When the discrete resistors are
replaced with XDCPs, we have a new structure called a Programmable
T-network.