An Inductorless 6-GHz Variable Gain Differential Transimpedance Amplifier in 0.18-μm SiGe BiCMOS

This paper presents a new inductorless 6-GHz variable gain differential transimpedance amplifier (VGDTIA) with voltage bias controlled variable gain designed using TowerJazz 0.18-μm SiGe BiCMOS technology (using CMOS only). It consists of a modified cross-coupled regulated cascode preamplifier stage (CCRGC) and a cascaded amplifier stage with bias-controlled gain-variation and third-order interleaving feedback (CVG3F). The design has a transimpedance gain range of 20.6-60.5 dBΩ with constant bandwidth of 6.6 GHz and a dynamic range of 41.2 μA to 1.1 mA. The power consumption is 33.9 mW from 1.8 V supply, and the input referred noise current is 10.4 pA/√Hz. This design is compact and the core area is 100 μm × 85 μm.

I. Introduction

Visible light communication (VLC) is expected to grow as the unused visible light spectrum (400 THz – 800 THz) increases in importance for wireless communication. The VLC system consists of a transmitter and receiver module with photodiodes to transmit and receive the light signal. In the receiver module, the transimpedance amplifier (TIA) is the first circuit block after the photodiode and converts its current output to voltage. As the first block, the TIA is critical for determining bandwidth, noise and dynamic range for the receiver module and entire VLC system [1]. Both CMOS and Si-BJT technology have been widely used for TIA designs due to their reliability at high frequency, low-cost and integrability with lasers for transmitters and photodetectors for receivers in the same wafer [1].