Wideband VGAs Using a CMOS Transconductor in Triode region

Abstract

Wideband variable gain amplifiers (VGAs) fabricated using 0.18 mum CMOS process are presented. A scheme with a CMOS triode transconductor is proposed to achieve linear-in-dB characteristics of VGAs for ultra wideband (UWB) systems. The implemented transmitter (TX) VGA shows a highly linear gain range of 28.4 dB (7 dB to -21.4 dB) and a bandwidth of 1200 MHz, while drawing only 2.7 mA from a 1.8 V power supply. The receiver (RX) VGA achieves a linear gain range of 73 dB and a bandwidth of 950 MHz while drawing 12.8 mA. The output P1dB varies from -8.5 dBm to -6 dBm. The TX and the RX VGA chips occupy areas of 0.2 times 0.2 mm and 0.6 times 0.2 mm, respectively