Techniques for maximizing input handling and improving linearity of gain interpolating VGAs

This work presents gain interpolating variable gain amplifier (VGA) design aspects. A technique is introduced to improve the VGA input handling capability from a few hundred millivolts to rail-to-rail without affecting any other performance parameters and with low complexity. An additional technique is proven by hand analysis and simulations to reduce the 3^rd order intermodulation products (IM3) of the VGA by 4dB. The VGA is designed in an IBM 0.13μm BiCMOS 7LM technology. It has a 56.5dB gain control range and draws 1.76mA from a 3V supply.