A Class-AB CMOS Variable Gain Amplifier for Low-Voltage Applications

A compact class-AB variable gain amplifier has been proposed. The amplifier structure is based on two-stage architecture comprising a linear transconductor cascaded by a class-AB current amplifier-based feedback transimpedance amplifier. The major advantage of such VGA circuit is its ability to offer a good degree of signal linearity without sacrificing the original advantages of its predecessor on both aspects of the power consumption and circuit complexity. Superiority of the proposed VGA has been confirmed by circuit simulation employing 0.18mum standard CMOS technology in designing a 10-MHz VGA under 0.5-V voltage supply with MOS's minimum threshold voltage of 0.43V while draining static power consumption less than 25muW.