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Lect2UP140_(100325)

Lect2UP140_(100325) - Lecture 140 The MOS Switch and Diode...

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Lecture 140 – The MOS Switch and Diode (3/25/10) Page 140-1 CMOS Analog Circuit Design © P.E. Allen - 201 LECTURE 140 – THE MOS SWITCH AND MOS DIODE LECTURE ORGANIZATION Outline • MOSFET as a switch • Influence of the switch resistance • Influence of the switch capacitors - Channel injection - Clock feedthrough • Using switches at reduced values of V DD • MOS Diode • Summary CMOS Analog Circuit Design, 2 nd Edition Reference Pages 113-124 Lecture 140 – The MOS Switch and Diode (3/25/10) Page 140-2 CMOS Analog Circuit Design © P.E. Allen - 201 Switch Model An ideal switch is a short-circuit when ON and an open-circuit when OFF. V C = controlling terminal for the switch ( V C high ± switch ON, V C low ± switch OFF) Actual switch: r on = resistance of the switch when ON r off = resistance of the switch when OFF V OS = offset voltage when the switch is ON I off = offset current when the switch is OFF I A and I B are leakage currents to ground C A and C B are capacitances to ground C AC and C BC = parasitic capacitors between the control terminal and switch terminals + V C A B I AB V AB R AB = 0 Ω ( V C = high) R AB = ∞Ω ( V C = low) 060526−03 060526-04 C AC C BC C A C B V C I A r OFF I OFF r ON C AB V OS A B C I B
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