Low-voltage Low-power CMOS IF Programmable Gain Amplifier

This paper presents a low-voltage low-power differential programmable gain amplifier (PGA) for wideband applications. To achieve low-voltage low-power and wideband operation while preserving linearity, the proposed cell is based on a g_m-boosted source-degenerated differential pair. Programmability is achieved combining two techniques, a switchable array of source degenerating hybrid polysilicon- MOS resistors and a programmable output current mirror. Designed in a 0.35 mum CMOS technology, the proposed PGA is very compact in terms of silicon area and consumes 0.5 mW from a single 1.8 V supply. The programmable gain varies linearly in-dB from 0 to 21 dB in 3 dB steps through a 4-bit word. Simulation results show an almost constant bandwidth of 100 MHz and total harmonic distortion figures are below -70 dB over the whole gain range at 10 MHz for a 0.2 V_p-p, differential output.