mixed_signal_notes_set_4

mixed_signal_notes_set_4 - ECE194J /594J notes, M. Rodwell,...

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Unformatted text preview: ECE194J /594J notes, M. Rodwell, copyrighted 2011 Mixed Signal IC Design Notes set 4: Broadband Design Techniques Mark Rodwell University of California, Santa Barbara rodwell@ece.ucsb.edu 805-893-3244, 805-893-3262 fax ECE194J /594J notes, M. Rodwell, copyrighted 2011 Getting more bandwidth At this point we have learned basics (MOTC etc) How can we get more bandwidth. ? Resistive feedback transconductance-transimpedance emitter-follower buffers, benefits and headaches emitter degenerationbasics emitter degeneration and area scaling ft-doubler stages.. distributed amplifiers broadbanding / peaking with LC networks. examples. ECE194J /594J notes, M. Rodwell, copyrighted 2011 Emitter Degeneration, I . / such that n combinatio RC an want instead we find will We . resistance emitter an only using introduced on was degenerati Emitter m be e e g C C R = Re Ce Re Re Ce ECE194J /594J notes, M. Rodwell, copyrighted 2011 Emitter Degeneration, 2 later.... back them add and removed, etc , ith can work w we such that is topology that the note Next cb bb C R Re Ce Re Ce Cbe gmVbe Vbe +- ECE194J /594J notes, M. Rodwell, copyrighted 2011 Emitter Degeneration, 3 ( ) change dont y back...the added be now can etc and ) 1 ( and ) / 1 /( So, cancel) terms dependent frequency that the (note * / 1 But ) ( so : Vbe from Working 1 2 1 3 3 2 1 cb bb E m be in in m E be E m be E E E be be m be m be be C R R g C j C j Z g R V I R g V C j R I V V C j g I V g I V C j I + = = + = = + = + = = = Re Ce Cbe gmVbe Vbe +- Ve Vb I1 I2 I3 ECE194J /594J notes, M. Rodwell, copyrighted 2011 Emitter Degeneration, Summary Re Ce Cbe gmVbe Vbe +- +- Rbb Ccbi Ccbx Rbb Ccbi Ccbx 1 ) 1 ( + = E m be in R g C C 1 , ) 1 ( + = E m m extrinsic m R g g g Other element values do not change... ECE194J /594J notes, M. Rodwell, copyrighted 2011 Emitter Degeneration, Unbypassed emitter resistance 1 , ) 1 ( + = E m m extrinsic m R g g g can be shown by elementary nodal analysis, work through Key observation: degeneration by this method results in a series input resistance, which can increase Cbe charging time. Rex Cbe gmVbe Vbe +- +- Rex Cbe gmVbe Vbe ECE194J /594J notes, M. Rodwell, copyrighted 2011 Emitter Degeneration, combination case Re Ce Cin gmextVin Vin +- Rex Ccbi Ccbx Rex Rbb Ccbi Ccbx Rbb Cbe gmVbe Vbe +- 1 ) 1 ( + = E m be in R g C C 1 , ) 1 ( + = E m m extrinsic m R g g g ECE194J /594J notes, M. Rodwell, copyrighted 2011 Emitter Degeneration and Area Scaling 1 [ ] L L ext m bb gen cb bb gen be L ext m V R R g R R C R R C a R g A + + + + + = = ) 1 )( ( ) ( have then we , gain a desire we If stage. CS he Consider t , 1 , emitter area =Ae current density =Je Current =Ae*Je=Ie transconductance=gm input capacitance=Cbe collector capacitance=Ccb base resistance=Rbb ECE194J /594J notes, M. Rodwell, copyrighted 2011 Emitter Degeneration and Area Scaling 2 Ce Re emitter area =Ae current density =Je Current =Ae*Je=Ie transconductance=gm input capacitance=Cbe...
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This note was uploaded on 12/29/2011 for the course ECE 594A taught by Professor Rodwell during the Fall '09 term at UCSB.

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mixed_signal_notes_set_4 - ECE194J /594J notes, M. Rodwell,...

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