Low Power CMOS Digital Variable Gain Amplifier Design For WiMAX/LTE Receiver

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This paper presents the design of a new Digital Variable Gain Amplifier cell (DVGA) that employs two transconductance amplifier and transimpedance amplifiers. The gain can be changed by used a digital control block, an auxiliary pair to retain a constant current density and offers a gain-independent bandwidth (BW). The proposed circuit has been presented to demonstrate the performance enhancement with the use of only one VGA stage for Worldwide Interoperability for Microwave Access (WiMAX) and Long Time Evolution (LTE) standards. The variable gain amplifier is designed for high gain, high bandwidth, low power consumption and low Noise Figure (NF). This circuit is implemented and simulated using device-level description of TSMC 0.18 u.m CMOS process. Simulation results show that the DVGA can provide a gain variation range of 43 dB (from 27 to -16 dB) with a 3 dB bandwidth over more than 166 MHz. The designed VGA circuit acquires a Noise Figure (NF) less than 19 dB, an Input Referred Noise (TRN) of around 4.2 nV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Hz and the Third Order Intercept Point measured at the Input (DZP3) of 8 dBm. The circuit consumes the maximum power 0.3 mW from a 1.8 V supply.