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

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

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<strong>III</strong>.3.a.iii Design of the Filters<br />

Two filters have been <strong>de</strong>signed, using high-performance <strong>Gm</strong>-cells. In the previous<br />

study, two <strong>Gm</strong>-cells show interesting assets. Filter 1 is based on a dynamic source<br />

<strong>de</strong>generation <strong>Gm</strong>-cell. This simple technique exhibits an interesting tra<strong>de</strong>-off noise versus<br />

linearity. Filter 2 is based on the MGTR technique. This technique <strong>de</strong>monstrates the best<br />

performances. These two filters are studied in the following and then compared.<br />

<strong>III</strong>.3.b <strong>Gm</strong>-cells with Dynamic Source Degeneration<br />

<strong>III</strong>.3.b.i <strong>Gm</strong>-cell Design<br />

Figure 125 <strong>de</strong>picts the <strong>de</strong>sign of the <strong>Gm</strong>-cell. As explained, circled in red on the figure<br />

is the dynamic source <strong>de</strong>generation of the transconductor which is ensured here by the use of<br />

NMOS transistors T5 to T8.<br />

Vin+<br />

Vout-<br />

T3<br />

T1<br />

Vb1<br />

T0<br />

- 106 -<br />

T2<br />

T4<br />

T5 T6 T7 T8<br />

Figure 125. <strong>Gm</strong>-cell <strong>de</strong>sign<br />

Vout+<br />

Vref<br />

CMFB<br />

Vin-

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