MOST Moderate–Weak-Inversion Region as the Optimum Design Zone for CMOS 2.4-GHz CS-LNAs

Abstract

In this paper, the MOS transistor (MOST) moderate-weak inversion region is shown to be the optimum design zone for CMOS 2.4-GHz common-source low noise amplifiers (CS-LNA) focused on low power consumption applications. This statement is supported by a systematic study where the MOST is analyzed in all-inversion regions using an exhaustive CS-LNA noise figure-power consumption optimization technique with power gain constraint. Effects of bias choke resistance and MOST capacitances are carefully included in the study to obtain more accurate results, especially for the moderate-weak inversion region. Noise figure, power consumption and gain versus the inversion region are described with design space maps, providing the designer with a deep insight of their trade-offs. The Pareto-optimal design frontier obtained by calculation, -showing the moderate-weak inversion region as the optimum design zone-is re-verified by extensive electrical simulations of a high number of designs. Finally, one 90-nm 2.4-GHz CS-LNA Pareto optimal design is implemented. It achieves the best FoM considering under-mW CS-LNAs published designs, consuming 684 µW, a noise figure of 4.36 dB, a power gain of 9.7 dB and an IIP3 of -4 dBm with load and source resistances of 50 Ω.

Short Channel Output Conductance Enhancement Through Forward Body Biasing to Realize a 0.5 V 250 0.6–4.2 GHz Current-Reuse CMOS LNA

“…The improvement in the g m /g ds due to FBB is clear, and it comes with no additional current consumption. It should be noted that in this analysis, the performance characterization of the device is studied in the MI region as this is the optimum region of operation for ULP and ULV designs [6], [23].…”

Gain compression improvement on low‐power cascaded current reuse LNAs

“…One of the operation regions is when RF MOS transistors are biased at V th vicinity, attaining the highest g m /I D ratio [14]. Another is the triode region, easily reached for a medium/high resistive load value (R L ), which is the case for high-gain designs.…”

“…The CS large-signal analytical study is feasible if a simple quasi-static I DS (V GS ) transfer characteristic, which fits the transistor behavior in the required operation regions, is found. One of the operation regions is when RF MOS transistors are biased at V th vicinity, attaining the highest g m /I D ratio [14]. Another is the triode region, easily reached for a medium/high resistive load value (R L ), which is the case for high-gain designs.…”

“…To obtain expression (12), it is required to solve (14) and find its closed-form solution in terms of V OVdc . Unfortunately, some sub-functions of equation (14) are mathematical expressions with no such closed-form solution.…”

“…Unfortunately, some sub-functions of equation (14) are mathematical expressions with no such closed-form solution. Instead, a numeric resolution method is applied to (14), and V OVdc values in terms of A in are calculated, where a known value is given to the remaining variables. Two different situations are plotted in Figure 6 Because the closed-form expression (12) could not be found, the only way to calculate I 1 behavior in terms of A in is resorting, once again, to MATLAB for compute expression (13).…”