哈工大模拟cmos第一章.ppt

绪论 Design of Analog Integrated Circuits Introduction Semi-conductor Device Physics and Model Outline 0. Introduction 1. MOS Device Physics and Model 0. Introduction Basic Circuit Theory: Analog Circuit Basic, Device Model, Foundation of Integrated Circuits Reference: Design of Analog CMOS Integrated Circuits (模拟CMOS集成电路设计)，[美]毕查德.拉扎维 著，陈贵灿 程军 张瑞智 等译，西安交通大学出版社。(英文版中文版) 集成电路设计 ，叶以正、来逢昌 著，清华大学出版社。 CMOS模拟电路设计（第二版）（英文版），[美] Phillip E. Allen, Douglas R. Holberg 著，电子工业出版社。 0.2 Design Flow of Analog IC 0.3 Analog and Mixed-signal IC 1. Device Physics 1.1 Basic 1.1.1 Structure of MOSFET 栅（G: gate）、源（S: source）、漏（D: drain）、衬底（B: bulk） MOSFET: 4-terminals device 1.1.2 MOS symbol 1.2 I/V characteristic of MOS 1.1.1 Threshold voltage （NFET） 耗尽depletion (b); 反型开始onset of inversion (c)； 反型inversion（d） Threshold （VTH） The VTH of an NFET is usually defined as the gate voltage for which the interface is “as much n-type as the substrate is p-type.” ( NFET的VTH通常定义为界面的电子浓度等于P型衬底的多子浓度时的栅压。) “native” VTH The native threshold value obtained from above equation may not be suited to circuit design, typically VTH=0±0.1V. It is typically adjusted bye implantation of dopants into the channel area during device fabrication. For NMOS，typically adjusted to 0.7V. 1.1.2 I/V of MOS device NMOS PMOS Cutoff region ID＝0 Triode（linear region） Saturation region 1.3 Second-order effects 1.3.1 Body effect For NMOS, when VBVS, As VB becomes more negative, Qd increases before an inversion layer is formed, thus VTH also increases. This is called the “body effect” or the “backgate effect”. 1.3.2 Channel-length modulation The actual length of the inverted channel gradually decreases as the potential difference of VDS increases. i.e. L’ is in fact a function of VDS. L’=L-ΔL， ΔL/L=λVDS λis the channel-length modulation coefficient. 1.3.3 Subthreshold conduction For VGS?VTH or VTH slightly, a ‘weak’ inversion layer still