Determine the required bias current and device sizes to design a source-coupled pair to have the following two characteristics. First, the small-signal transconductance with zero differential input voltage should be 1.0 mA/V. Second, a differential input voltage of 0.2 V should result in a differential output current of 85 percent of the maximum value. Assume that the devices are n-channel transistors that are made with the technology summarized in Table 2.4. Use a drawn device channel length of 1µm. Neglect channel-length modulation, and assume X_d= 0.

Table 2.4:

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Value Value p-Channel n-Channel Units Parameter Symbol Transistor Transistor 5 x 105 4 x 106 Substrate doping Atoms/cm NA, Np Gate oxide thickness 80 80 lox Metal-silicon work function Фия -0.6 -0.1 cm/V-s Channel mobility Minimum drawn channel 450 150 Lárwn 0.4 0.4 um length Source, drain junction depth Source, drain side diffusion Overlap capacitance per unit gate width Threshold adjust implant (bох dist) impurity type effective depth effective surface 0.15 0.18 um La 0.09 0.09 um 0.35 0.35 fF/um х, Nsi 0.16 0.16 um Atoms/cm 3 x 1016 4 x 1016 concentration Nominal threshold voltage Polysilicon gate doping concentration Poly gate sheet resistance Source, drain-bulk junction capacitances (zero bias) Source, drain-bulk junction capacitance grading V, Napoly 0.6 1020 -0.8 Atoms/cm? 1020 R, Cp fF/um? 0.2 0.4 0.5 0.4 coefficient Source, drain periphery capacitance (zero bias) Source, drain periphery capacitance grading fF/um С рио 1.2 2.4 0.4 0.3 п coefficient Source, drain junction built-in potential 0.7 0.7 Oss Surface-state density 10" 10" Atoms/cm PXP dV ps Channel-length modulation 0.02 0.04 um/V parameter