Analysis of the Bridged T-Coil Circuit Using the Extra-Element Theorem

The bridged T-coil (BTC) circuit is often employed to extend the bandwidth of a wideband amplifier beyond the transition frequency fT of the driver device. Although the optimal design solution is well known, extreme algebraic complexity has caused its derivation to remain arcane. This brief presents an analysis of the BTC circuit using the extra element theorem which breaks the overall problem down into a series of simple network analyses and produces the final result as the product of the transfer function without the "extra element" and a multiplicative correction factor. The design is completed by using pole-zero cancellation to reduce the order of the transfer functions