Low-noise, low-distortion CMOS AM wide-band amplifiers matching a capacitive source

A low-noise, low-distortion AM wideband CMOS amplifier that matches a capacitive antenna is presented. The amplifier uses a single-ended input stage to realize optimal noise matching with a capacitive source of 75 pF. The equivalent input noise voltage is as low as 0.7 mu V/sub rms/ within 2.5-kHz IF (intermediate frequency) bandwidth. A differential symmetrical class-AB output stage is optimized to large-scale signal distortion performance. With an 8-V single-power supply the amplifier is capable of driving a 7-V/sub pp//1-MHz signal into a 400- Omega load with a total harmonic distortion of 2%. A very high dynamic range of 130 dB has thus been achieved. An intermodulation-free dynamic range up to 96 dB and an IM3 intercept of 18 V/sub pp/ have been measured. The amplifier is fabricated in a standard 3- mu m n-well CMOS technology. Design details concerning noise, distortion, and stability performance are analytically described.<
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