第26卷第6期 半导体学报 Vol.26 No.6 2005年6月 CHINESE JOURNAL OF SEMICONDUCTORS June,2005 Analysis and Optimum Design of Differential Inductors Using Distributed Capacitance Model* Jian Hongyan,Tang Zhangwen,He Jie,and Min Hao (State Key Laboratory of ASIC &System,Fudan University,Shanghai 200433,China) Abstract:A distributed capacitance model for monolithic inductors is developed to predict the equivalently parasitical capacitances of the inductor.The ratio of the self-resonant frequency (fsR of the differential-driven symmetric in- ductor to the fse of the single-ended driven inductor is firstly predicted and explained.Compared with a single-ended configuration,experimental data demonstrate that the differential inductor offers a 127%greater maximum quality factor and a broader range of operating frequencies.Two differential inductors with low parasitical capacitance are developed and validated. Key words:distributed capacitance model;self-resonant frequency ratio;quality factor;differential inductor:op- timum design EEACC:2140;2530B;2550F CLC number:TN405 Document code:A Article ID:0253-4177(2005)06-1077-06 erties (e.g.power supply noise rejection).A sym- 1 Introduction metric inductor consumes less chip area as com- pared to single-ended equivalents when used in a A monolithic inductor is an important compo- typical circuit.A symmetric inductor that is excited nent in highly integrated radio frequency circuits differentially (also called a differential inductor) (RF ICs)for wireless communication systems.But can realize a substantially greater factor without al- a monolithic inductor has a low quality factor Q tering the fabrication process[2). due to metal ohmic loss and conductive silicon sub- The distributed capacitance model(DCM)for strate loss.Many researchers found quite a few monolithic inductors,which is for a single-ended methods to improve the Q of the monolithic induc-inductor but not for the differential inductor has tor[].The Q and fsr (self-resonant frequency)are been studied in recent years[s-5]. the two most important parameters of the mono- In this paper,from the view of the parasitical lithic inductor.The lower parasitical capacitance capacitance of the inductor,the reason for a differ- the inductor has,the higher Q and fsr are. ential inductor with both a higher Q and fsr is ana- It should be noted that the differential circuits lyzed and firstly interpreted by DCM.Two differ- (amplifiers,mixers,and oscillators)are commonly ential inductors with the low equivalently parasit- used in monolithic transceiver designs because of ical capacitances (Cmm)between the two terminals their robustness and superior noise rejection prop-are developed and validated. Project supported by the Shanghai Science 8.Technology Committee(No.037062019) Jian Hongyan male.PhD candidate.He is interested in monolithic inductor and antenna optimization,RF circuits design such as LNA.mixer. and VCO,and antenna design for RFID.Email:hyjian@fudan.edu.cn Received 14 November 2004,revised manuscript received 1 February 2005 2005 Chinese Institute of Electronics第-0卷 第0期 -’’/年0月 半 导 体 学 报 OQ!$J"JI+VZ$UN+D"JW!O+$BVO<+Z" ‘9@,-0 $9,0 IG7>!-’’/ #[F9T>:42G??9F4>CH348>"867L865":5>7:>h <>:879@9L3O9;;544>>"$9,’(%’0-’).# I567Q97L367 ;6@>![8B:67C5C64>,Q>52574>F>24>C57;979@5485:57CG:49F67C674>7769?45;5^64597!ZD:5F:G542C>25L72G:862N$U!;5R>F! 67C‘O+!67C674>776C>25L7A9FZD!B,J;65@$83T567!AGC67,>CG,:7 Z>:>5\>C)*$9\>;H>F-’’*!F>\52>C;67G2:F5?4F>:>5\>C)D>HFG6F3-’’/ "-’’/O857>2>!72454G4>9AJ@>:4F975:2 "<B9H@I@B<K%C>IP;P$=@IX<8L$ILL=?=<>IB9’<K;M>8?@ )@I<X$I@>?IJ;>=K/BCBMI>B<M=68K=9# I567Q97L367!<67LP867L=>7!Q>I5>!67CW57Q69 "!J/J)*)8-/F0M/J0M80DL!Q. 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