A diode is a semiconductor device which allows current to flow through it in only one direction. Although a transistor is also a semiconductor device, it does not operate the way a diode does. A diode is specifically made to allow current to flow through it in only one direction. | Digital Integrated Circuits A Design Perspective The Devices Jan M. Rabaey Anantha Chandrakasan Borivoje Nikolic July 30, 2002 Goal of this chapter Present intuitive understanding of device operation Introduction of basic device equations Introduction of models for manual analysis Introduction of models for SPICE simulation Analysis of secondary and deep-sub-micron effects Future trends The Diode n p p n B A SiO 2 Al A B Al A B Cross-section of pn -junction in an IC process One-dimensional representation diode symbol Mostly occurring as parasitic element in Digital ICs Depletion Region Diode Current Forward Bias Typically avoided in Digital ICs Reverse Bias The Dominant Operation Mode Models for Manual Analysis Junction Capacitance Diffusion Capacitance Secondary Effects – – – V D (V) – I D ( A ) 0 0 Avalanche Breakdown Diode Model SPICE Parameters What is a Transistor? A Switch! |V GS | An MOS Transistor The MOS Transistor Polysilicon Aluminum MOS Transistors . | Digital Integrated Circuits A Design Perspective The Devices Jan M. Rabaey Anantha Chandrakasan Borivoje Nikolic July 30, 2002 Goal of this chapter Present intuitive understanding of device operation Introduction of basic device equations Introduction of models for manual analysis Introduction of models for SPICE simulation Analysis of secondary and deep-sub-micron effects Future trends The Diode n p p n B A SiO 2 Al A B Al A B Cross-section of pn -junction in an IC process One-dimensional representation diode symbol Mostly occurring as parasitic element in Digital ICs Depletion Region Diode Current Forward Bias Typically avoided in Digital ICs Reverse Bias The Dominant Operation Mode Models for Manual Analysis Junction Capacitance Diffusion Capacitance Secondary Effects – – – V D (V) – I D ( A ) 0 0 Avalanche Breakdown Diode Model SPICE Parameters What is a Transistor? A Switch! |V GS | An MOS Transistor The MOS Transistor Polysilicon Aluminum MOS Transistors - Types and Symbols D S G D S G G S D D S G NMOS Enhancement NMOS PMOS Depletion Enhancement B NMOS with Bulk Contact Threshold Voltage: Concept The Threshold Voltage The Body Effect Current-Voltage Relations A good ol’ transistor Quadratic Relationship 0 1 2 0 1 2 3 4 5 6 x 10 -4 V DS (V) I D (A) VGS= V VGS= V VGS= V VGS= V Resistive Saturation VDS = VGS - VT Transistor in Linear Transistor in Saturation Pinch-off Current-Voltage Relations Long-Channel Device A model for manual analysis Current-Voltage Relations The Deep-Submicron Era Linear Relationship -4 V DS (V) 0 1 2 0 1 2 x 10 I D (A) VGS= V VGS= V VGS= V VGS= V Early Saturation Velocity Saturation x (V/µm) x c = u n ( m / s ) u sat = 10 5 Constant mobility (slope = µ) Constant velocity Perspective I D Long-channel device Short-channel device V DS V DSAT V GS - V T V GS = V DD ID versus VGS 0 1 2 0 1 2 3 4 5 6 x 10 -4 V GS (V) I D (A) 0 1 2
