A Differential 3.3V BICMOS Buffer with Current Consumption and Linearity Control for RF Mixer

A design of a 3.3 Volts BiCMOS buffer with current consumption and linearity control is presented. This buffer with a low output impedance is fully differential and designed to be used with RF (radio frequency) mixer in low IF (intermediate frequency) architecture. The proposed buffer is directly connected to the output of the RF mixer and designed to drive off- chip low impedance load as SAW (surface acoustic wave) or discrete differential filters. A good flexibility is obtained about the control of the linearity performance with the possibility to adjust the power consumption. The linearity and current consumption are independently adjustable and an optimum of the 3rd order linearity performance is achieved for each current consumption value. A schematic of the differential Bi-CMOS 3.3 volts buffer is proposed and some linearity simulation results are presented and discussed in terms of output IM3 level and current consumption. The results show a saving of half power in comparison with a buffer with no linearity control for the same output IM3 level.