On the high-frequency limitations of active ladder networks

High-frequency limitations of a generalized immittance converter (GIC) and leapfrog (coupled-biquad) ladder structures are compared. It is shown that the high-frequency limitations of GIC derived -active ladder filters are improved very significantly by employing simulated-inductance and/or frequency-dependent negative resistance (FDNR) elements for which the factor is made virtually independent of the gain-bandwidth products of the two operational amplifiers in each GIC. The behavior of such GIC derived structures with respect to variations in temperature is further improved by using dual operational amplifiers for each GIC instead of individual ones.