A 75dB Programmable Gain Amplifier for Dual Mode Wireless Receivers

In this paper, a programmable gain amplifier (PGA) is designed and implemented for GPS/Galileo and WCDMA dual mode receiver using TSMC 0.18μm CMOS technology. The 0-75dB variable gain range is obtained by cascading a 0-15dB variable gain stage and four 15dB fixed gain stages. An open-loop structured fully-differential amplifier with source feedback resistor is adopted in basic gain stage. Variation of gain is achieved by switch-controlled output resistor network. Gm-boost structure is used in main amplifier. A DC-offset canceller circuit using DC negative feedback technique is proposed to eliminate the DC-offset of the PGA. Post-simulation shows that the PGA has 0-75dB variable gain range, 1dB gain resolution and less than 0.3dB gain error; the minimum DC attenuation is about 15dB over the whole gain range; -3dB bandwidth at the maximum gain configuration is about 15MHz; differential output peak to peak voltage is greater than 1V; and the entire circuit consumes about 3.6mA current under 1.8V supply voltage.