BICMOS transconductor differential stage for high-frequency filters

摘要

A BiCMOS Transconductor differential stage (10) for high frequency filters comprises an input circuit portion having signal inputs (IN+,IN-) and comprising a pair of MOS transistors (M1,M2) having their respective gate terminals (G1,G2) corresponding to the signal inputs as well as an output circuit portion having signal outputs (OUT-,OUT+) and comprising a pair of two-pole transistors (Q1,Q2) connected together with a common base in a circuit node (B) and inserted between inputs (IN+,IN-) and outputs (OUT-,OUT+) in cascode configuration. The stage (10) in accordance with the present invention calls for a switching device (3) associated with at least one of said added two-pole transistors (Q1,Q2) to change the connections between the parasite capacitors present in the transconductor stage. The switching device (3) also comprises at least one added two-pole transistor (Q1x, Q2x) connected in a removable manner in parallel with the corresponding two-pole cascode transistor (Q1,Q2).;In a variant embodiment there are also provided respective added MOS transistors (M1x,M2x) connected in parallel with the MOS transistors (M1,M2) of the input portion to change the ratio W:L of each of the input transistors (M1,M2).