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

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

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

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Figure 130 confirms the transconductance of the <strong>Gm</strong>-cell which is 10mS at the<br />

working frequency. Its voltage gain is typical of a lossy integrator. DC voltage gain is 22.5dB.<br />

Gain then <strong>de</strong>creases with frequency due to the capacitive load.<br />

Figure 130. <strong>Gm</strong>-cell DC gain and transconductance<br />

Figure 131 shows the loa<strong>de</strong>d <strong>Gm</strong>-cell variations as a function of the voltage bias of the<br />

pseudo-differential pair. Switching-off the PDA, which corresponds to a PDA bias of 0V, the<br />

<strong>Gm</strong>-cell IIP3 is 9dBm. Disconnecting the PDA leads to a comparable value (9.4dBm).<br />

However, on a peak of linearity close to 350mV, the specified 20dBm are reached. This<br />

technique is then able to enhance the <strong>Gm</strong>-cell linearity by up to 12dB.<br />

Figure 131. <strong>Gm</strong>-cell linearity versus PDA bias<br />

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