III. Gm-C Filtering - Epublications - Université de Limoges

However, Figure 119 shows that this high linearity level is reached on a linearity peak
for the PDA bias. As soon as the PDA bias drifts from its original value, the IIP3 of the Gmcell
is drastically reduced.
Figure 119. Transconductance linearization by MGTR
III.2.g Transconductance Linearization Techniques Comparison
Table 8 summarizes the linearity performances obtained using the different
linearization techniques, as well as the advantages and drawbacks of each. To make
quantitative comparisons, performances are simulated at 100MHz. The Gm-cells are studied
with a capacitive load CL (see Figure 120) which depends on the gm value to keep the same
g m
ratio.
C
Figure 120. Gm-cell test bench
The Gm-cell DC voltage gain is set close to 22.5dB as explained further. Hence, all
gm, r0 and C parameters are equal or comparable. Furthermore, at 100MHz, it should be
underlined that the Gm-cell voltage gain is close to 0dB.
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