Transconductance Boosting Technique for Bandwidth Extension in Low-Voltage and Low-Noise Optical TIAs

Abstract

This brief presents a TIA topology with an active feedback path and a current bleeding circuit to relax the tradeoffs among gain, bandwidth and headroom limitations in a low voltage design. Using a two-stage common-source amplifier in the feedback path creates adequate degrees-of-freedom in the design for lowering the input resistance of the TIA and proving the bandwidth without degrading the amplifier gain. Analysis of the TIA transfer function and noise provide design guidelines for a well-behaved time response and low input-referred current noise. To demonstrate efficiency of the proposed technique, two designs in 0.18 µm CMOS technology with different values of the input capacitor are presented. The comparison of the designs with two categories of TIAs reported in the literature validates effectiveness of the presented transconductance boosting technique and demonstrates the flexibility of the proposed topology for different applications with a vast variety of the capacitance values at the TIA input.