'Institute of Electrical and Electronics Engineers (IEEE)'
Abstract
This work reports a modified regulated cascode (RGC) transimpedance amplifier (TIA) with tolerance to the ultra-high photodiode capacitances encountered in visible light communication systems. The new design is proposed to ameliorate internal miller capacitance limiting effects, inherent in traditional RGC designs through the use of a cascode circuit within the RGC. The paper introduces the design principle of the proposed RGC and presents derivation of tractable mathematical equations for describing the operation. The bandwidth advantage of the new design is shown through comparing the operation of the modified circuit to the traditional one using full circuit simulations. The paper presents full circuit designs, based on discrete components and printed circuit board (PCB) construction of both circuits and contrasts their operation, experimentally demonstrating bandwidth advantage for different values of photodiode capacitances and amplifier transimpedance gain values. Measurements show that using the modified RGC TIA results in a bandwidth improvement of over 200 % relative to the conventional RGC design, achieving a bandwidth of 200 MHz at 2mathrm{K} transimpedance gain with a 300 pF photodiode capacitance. As such, this is one of the highest bandwidths reported for such high capacitances, to-date
