A new 1.2 V BiCMOS log-domain integrator for companding current-mode filters

New structures of differential and single-ended log-domain integrators are proposed, which can be used for very low supply voltage continuous-time filters. They offer a tuning range of several decades and operate at minimum supply voltages down to 1 V. The single-ended version allows very simple filter structures, whereas the differential one can be driven by signal currents which are much larger than the bias currents (class AB operation).