T09 OTA_sss.pdf - bSpace
T09 OTA_sss.pdf - bSpace
T09 OTA_sss.pdf - bSpace
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• Phase 1:<br />
– sample V i onto C s :<br />
SC Gain Stage<br />
ϕ1<br />
– Q s = V i * C s<br />
– Null charge on C f<br />
• Phase 2:<br />
– Amplifier “moves”<br />
charge from C s to C f :<br />
– Q f = Q s = V i * C s<br />
vi<br />
ϕ2<br />
ϕ1<br />
C f<br />
ϕ1<br />
ϕ2<br />
C i<br />
vx<br />
1mS<br />
C f<br />
C L<br />
vo<br />
– V out = Q f / C f<br />
= V i * C s / C f<br />
• Implement switches with MOSFETs. Drive with “2-phase nonoverlapping<br />
clock”.<br />
• Gain set by capacitor ratio (precise). Output valid only at end<br />
of phase 2 and during phase 1.<br />
• Cannot drive resistive load.<br />
EECS 240 Topic 9: <strong>OTA</strong><br />
© 2007 B. Boser & A. Niknejad
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