1.25V direct-conversion CMOS transmitter front-end for 900MHz ZigBee applications

This paper presents a very low power direct-conversion up-mixer and driver amplifier. The designed mixer is based on the typical Gilbert-cell, and the driver amplifier uses a folded cascode topology to improve the linearity under the low supply voltage. The fabricated up-mixer shows 5.5dB of conversion gain and 7.5dBm of output IP3, and the driver amplifier shows 17dB of power gain and 12dBm of output IP3. The up-mixer and driver amplifier consume 4.5mA and 2mA from 1.25V supply, respectively.