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Unformatted text preview: chlib.nsf/techdocs/FE154539B8C4C01687256CD9007346D7/$file/180nmCMOS32404.pdf EECS 240 Lecture 2: CMOS  passive devices © 2006 A. M. Niknejad and B. Boser 35 Passives EECS 240 Lecture 2: CMOS  passive devices © 2006 A. M. Niknejad and B. Boser 36 www.ibm.com/chips/techlib/techlib.nsf/techdocs/FE154539B8C4C01687256CD9007346D7/$file/180nmCMOS32404.pdf Distributed Effects
• Can model IC resistors as
distributed RC circuits.
• Transmission line analysis
yields the equivalent 2port parameters.
• Inductance negligible for
small IC structures up to
~10GHz.
EECS 240 Lecture 2: CMOS  passive devices © 2006 A. M. Niknejad and B. Boser 37 Effective Resistance • Rsh = 100 Ω/□, Cx=3.45×105 F/m2
• 10kΩ resistor drops to 5kΩ at 1 GHz ! (W=5µ)
• High frequency resistance depends on W. Need
distributed model for accurate freq response.
EECS 240 Lecture 2: CMOS  passive devices © 2006 A. M. Niknejad and B. Boser 38 Capacitor Q • Current density in capacitor plates drops
due to vertical displacement current.
• Must analyze the distributed RC circuit…
EECS 240 Lecture 2: CMOS  passive devices © 2006 A. M. Niknejad and B. Boser 39 Capacitor Impedance
• For a capacitor contacted at one side, we
can show that • We can simplify this for small structures EECS 240 Lecture 2: CMOS  passive devices © 2006 A. M. Niknejad and B. Boser 40 Double Contact Strucutre • Instead of doing distributed analysis, we can guess the
current distribution as linear and quickly calculate the
effective resistance.
• For a double contact case, the resistance drops by 4 times.
EECS 240 Lecture 2: CMOS  passive devices © 2006 A. M. Niknejad and B. Boser 41 OnChip Inductors • Once in the domain of RF circuits, now inductors
are finding applications in wideband design (e.g.
shunt peaking).
• By proper design, the bandwidth of the RC circuit
can be boosted by 85% (20% peaking).
EECS 240 Lecture 2: CMOS  passive devices © 2006 A. M. Niknejad and B. Boser 42 Spiral Inductors • These inductors are small (0.110 nH) and are used widely
in RF circuits.
• Use top metal for high Q and high self resonance
frequencies. Very good matching and accuracy.
EECS 240 Lecture 2: CMOS  passive devices © 2006 A. M. Niknejad and B. Boser 43 MultiLayer Inductors Top view 3D view (not to scale) • By taking advantage of multiple metal layers and
mutual coupling, we can realize very large
inductors (~ 100 nH).
EECS 240 Lecture 2: CMOS  passive devices © 2006 A. M. Niknejad and B. Boser 44...
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 Spring '04
 Boser
 Computer Science, Integrated Circuit

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