Demonstration of Negative Impedance Conversion for Bandwidth Extension in VLC

This work proposes and demonstrates the utility of a negative impedance converter (NIC) circuit, based on a common collector (CC) amplifier, for the generation of negative capacitance. The design principle of the proposed NIC is introduced, then a negative capacitance equals −200 pF is demonstrated using discrete devices constructed on a printed circuit board (PCB). The designed NIC is applied for the bandwidth extension of LEDs to enhance the achievable data rates in visible light communication (VLC) systems. The paper includes analytical derivations of the obtained negative capacitance as a function of circuit parameters and verifies this by both simulation and experimentally. Measurements show significant bandwidth extension by neutralising the bandwidth-limiting effect of the LED diffusion capacitance through the introduction of a parallel negative capacitance.