Extended-Bandwidth Negative Impedance Converters by Nested Networks

Abstract

We show a novel scheme for increasing resistive bandwidth in opamp negative impedance converters (NICs) with recursive topologies. A simplified theoretical model indicates bandwidth improvement due to altering pole and zero locations in the network’s transfer function by allowing certain resistor terms to take negative values. We extend established practices by allowing negative resistors as NIC components by nesting NICs within an NIC network. The result is a nested arrangement of NICs that theoretically extends frequency-dependent terms in the model’s transfer function toward higher frequencies. This theory is confirmed experimentally by comparing nested networks to standard NIC networks. Improvement is limited by non-ideal amplifier effects and comes at the price of system complexity. This brief provides techniques for nesting voltage-mode NICs to increase bandwidth of negative resistance in NIC opamp circuits by a factor of 1.65–3.24.