A 0.25dB gain step high linear programmable gain amplifier

A 0.25dB gain step high linear and accurate digitally programmable gain amplifier (PGA) is presented in this paper. The PGA consists of a coarse stage PGA, a fine stage PGA and a buffer. The voltage gain of the coarse PGA can be changed from -6dB to 17dB with 1dB steps and has a -3dB bandwidth of 35MHz. In order to optimize the linearity and gain accuracy, a new structure resistor array is proposed to realize the 0.25dB step fine PGA. The fine PGA shows a dB-linear range of 11.75dB (-5.75dB to 6dB) with a gain error of less than 0.09dB. The proposed PGA circuit is designed in a 0.18um CMOS process and the simulation results show that the PGA has the output-referred third-order interception (OIP3) of 39.7dBm and THD of -79.84dB at -1dBV
_p-p
output voltage, with a current consumption of 2.2mA from a 1.8V supply.