An Ultra-Wideband Amplifier With Compact Magnetically Coupled Feedback Gain Cell

This paper proposes a magnetically coupled feedback (MCF) gain cell to enhance the gain bandwidth product (GBW) of an amplifier at a small chip area cost. The MCF gain cell achieves a GBW enhancement ratio of 4.1Sx with 0.5 dB gain ripple compared to the basic RC topology. Meanwhile, thanks to the MCF topology, the shunt peaking inductors in the adjacent stages can be combined into one inductor floorplan to save chip area. Besides, the compact solenoid inductor is employed to further decrease the chip area. The proposed MCF gain cell is used in an ultra-wideband prototype amplifier, which is implemented in a 65-nm CMOS technology. The prototype amplifier occupied only 0.053 mm² chip area, and the power consumption is 72 mW at a supply of 1.8 V. The amplifier realizes a DC gain of 27 dB and a 3-dB bandwidth of 30.8 GHz. Moreover, the in-band gain and group delay ripple are only 0.8 dB and 17 ps, respectively.

I. Introduction

In the past decades, the explosive growth of communication data rate has generated tremendous demand for wideband transceivers, in which the wideband amplifier is an essential building block. Meanwhile, the trend toward full integration of transceivers makes CMOS technology an excellent candidate. Unfortunately, the intrinsic capacitance of the active device in CMOS technology restricts the bandwidth of the amplifiers. To push the bandwidth beyond such a limit, several bandwidth extension techniques have been proposed [1]–[6].