Variable Gain Amplifier Based on MIFGMOS Transistor for Low Voltage Applications

This paper introduces a method for designing a fully balanced Variable Gain Amplifier (VGA) depending on a trans-conductance variation and switched feedback resistance. In this method, the Floating Gate MOS transistor is used as a variable current source. Consequently, the trans-conductance of the gain MOS transistor is varying which is affecting the overall gain. Switching feedback resistance is varying the current which in turn affects the gain range. The proposed strategy is suitable for low voltage applications since the threshold voltage of the floating transistor can be adjusted. Power mitigation and linearity are developed in the variable gain amplifier stage. A simple common source and a fully balanced differential VGA are considered to illustrate the concept. The VGA circuit is designed and simulated using the 0.13μm CMOS process; the overall VGA consumes 1.3mA from a 1.8V supply. The VGA achieves gain variation depending on control voltage and feedback resistance with bandwidth up to 1MHz.