CMOS Transimpedance Amplifiers for Biomedical Applications: A Comparative Study

Recently, different medical devices have emerged and utilized in a numerous health care fields such as pulse oximetry, cuffless blood pressure using Photoplethysmogram (PPG), noninvasive blood glucose measuring, and Near Infrared Spectroscopy (NIRS). Those devices are very similar in their analog front end circuit which is a transimpedance amplifier (TIA). Many different TIA topologies have appeared in different optoelectronic fields which make the choice of the best TIA topology for a certain application a challenging task. In this regard, this paper presents a comparison between state of the art, previously published TIA topologies. All topologies are simulated at four different simulation cases to account for various design scenarios. The topologies are simulated with 10 pF photodiode (PD) input capacitance and 5 KHz bandwidth (BW) while optimizing for two different targets; one time for minimum input noise and the other for minimum power consumption. Moreover, the same procedures are performed with 2 pF PD and 100 MHz BW to account for higher BW demanding applications. The studied topologies are compared according to their transimpedance gain, power consumption, total input referred noise current, and dynamic range (DR) to expose their relative merits. A noise and a transimpedance gain mathematical models are also presented for each topology to assist the comparison. Recommendations to designers on which TIA to select in a certain application are concluded according to the obtained results.