A high bandwidth modified regulated cascode TIA for high capacitance photodiodes in VLC

This work reports a modified regulated cascode (RGC) amplifier which, when used as a transimpedance amplifier (TIA), improves tolerance to ultra-high photodiode capacitances encountered in some optical communications applications. When a conventional RGC is used as a TIA the Miller capacitance, introduced by the base-collector capacitance of its common base stage, limits bandwidth and compromises stability. Such undesirable characteristics are simply eliminated by introducing an additional cascode stage that nullifies the Miller capacitance. We show that exceptional improvement in bandwidth can be made, which is important for visible light communication systems, where using large-area (large capacitance) photodiodes is desirable