Frequency-Response Analysis and Design Rules for Capacitive Feedback Transimpedance Amplifier

Abstract

Precision instrumentation systems, such as optical receivers and other current-output measurement systems, often contain a transimpedance amplifier (TIA). The commonly used resistive feedback TIA (RF-TIA) has a drawback in its practical implementation; the system bandwidth is limited by the feedback resistor and its parasitic capacitance in high-speed applications. To overcome this drawback, a capacitive feedback TIA (CF-TIA) can be used. The gain and bandwidth performance of the CF-TIA are theoretically equivalent to those of the RF-TIA. Although CF-TIA has been introduced in previous studies for reducing thermal noise and addressing the difficulty in integrating a high resistance with the CMOS technology, past analyses have not been in sufficient depth. The ultimate goal of this study is providing designers in this field with helpful design rules and analytical tools. In particular, a transfer function model, the critical design parameters, and a stability analysis are presented. Furthermore, a new CF-TIA configuration involving a simplified integrator dc-feedback loop is introduced, which can be deployed as a single stage rather than the conventional two-stage topology. While the applications considered in this study were high-speed sensor measurements and devices with a high input capacitance, such as a laser position detector, the analytical results obtained herein are also applicable to a variety of other applications such as emerging biosensors and optical communication system.