Digitally Controlled PGA for Low Power Applications

A digitally controlled PGA with 46µW power dissipation and 1-40dB programmable voltage gain in 2dB steps is presented in this paper. It is best suited for low power applications. It has low input referred noise i.e. 2.9µV/√Hz, 3.4µV/√Hz and 1.8µV/√Hz at 1Hz, 50Hz and 200Hz respectively. The PGA has 3dB bandwidth of 20 KHz. It has PSRR that exceeds 84.5dB at all gain settings and is constant for entire 20 KHz bandwidth. In order to achieve linearity in programmable gain a new structure resistor array is proposed. The resistance is implemented by using floating active resistors which act as resistor. The advantage of floating active resistor is that they have small size and their resistance can be easily altered by changing the W/L ratios. In this work the values of floating resistor (rds) is between 180Ω-23KΩ to achieve desired gain and low power dissipation. This PGA is designed and simulated in 0.18µm technology. The simulation and layout results are obtained using Cadence’s Virtuoso and Sparta tool.