A Precise Decibel-Linear Programmable Gain Amplifier Using a Constant Current-Density Function

In this paper, a compensation technique for realizing a precise decibel-linear CMOS programmable gain amplifier (PGA) is described. The proposed PGA, employing an auxiliary pair, not only retains a constant current density but also offers a gain-independent bandwidth (BW). For verification, a compact PGA (0.1 mm²) is fabricated using a 0.13-μm CMOS process and measured. The measured gain control range is from -16 to + 32 dB with 6-dB steps, while the error deviation of the gain is less than 0.35 dB. A constant 3-dB BW of 60 MHz and an input P_1dB of -35 to -5 dBm are obtained, while dissipating a lower power of 1.2 mW under a 1-V supply.