CMOS Analog Integrated Circuit
CMOS Analog Integrated Circuit Zou Zhige Spring, 2008
Information •
Required text — Razavi《Design of Analog CMOS Integrated Circuits》
•
Reference — Gray《Analysis and Design of Analog Integrated Circuits, 4th》 — Hspice Handbook（Please download from http://icc.hust.edu.cn）
•
Assignments — Lecture 32 hours，Project design 8 hours
•
Course Grade Composition — Homework 10％，Design Project 20％，Final Exam 70％
•
Question — Please Email to [email protected] , or phone 13377878863 — Assistant: 高专 (13297967279), Email: [email protected] Zou Zhige
RCVLSI&S
2
Circuit Simulation • Primary tools: HSpice/AWaves • Course Technology – 0.35μm CMOS –Spice model is provided at http://icc.hust.edu.cn • Caution — Spice is nothing but a "calculator" that lets you evaluate and test your ideas — There is no need to simulate anything unless you already know the (approximate) answer!
Zou Zhige
RCVLSI&S
3
Course Topics • Introduction to Analog Design • CMOS technology and device models • Single-stage amplifiers • Differential pairs • Current sources and mirrors, active loads • Frequency Response of Amplifiers
Zou Zhige
RCVLSI&S
4
Overview • Reading – Chapter 1 (p1-8) •
Introduction – In this first lecture, we will introduce “Why CMOS Analog Integrated Circuit?” and “General Concepts in Analog Design.”
Zou Zhige
RCVLSI&S
5
1.1 why Analog？(1) 1.1.1 Analog signals versus Digital signals: • Signal: A signal will be considered to be any detectable value of voltage, current, or charge. A signal should convey information about the state or behavior of a physical system. • Analog signal is a signal that is defined over a continuous range of time and a continuous range of amplitudes. • Digital signal is a signal that is defined only at discrete values of amplitude, or said another way, a digital signal is quantized to discrete values. Zou Zhige
RCVLSI&S
6
1.1 why Analog？(2) Advantages of Digital signal processing compared with analog signal processing: – Robustness: digital signal processing is insensitive to process variations, supply voltage change, temperature variation, interference, and aging; – Programmability: digital signal processing algorithms can be changed fairly easily by changing the coefficients or the software codes; – Flexibility: some signal processing algorithms have extra degree of freedom if implemented in digital, such as linear phase filter. Zou Zhige
RCVLSI&S
7
1.1 why Analog？(3) Digital System Exist Today: – Digital Mobil Phone; – Digital Film; – Digital TV; – Digital Power Amplifier; – Digital filter; – Digital ……
Almost every thing is Digital . So, Analog is out of date? Zou Zhige
RCVLSI&S
8
1.1 why Analog？(3) 1.1.2 why Analog？ As many applications have moved to digital domain, analog circuits seem obsolete. But actually analog circuit designers are in strong demand today. Why?!!! The physical world is in analog (at macroscopic level), such as · The output signals of many signal sources are all in analog form; · The RF signals in space and at the antenna are also in analog.
Zou Zhige
RCVLSI&S
9
1.1 why Analog？(4) We need · Analog-to-digital converters (ADC) to digitize the input signal, · Digital-to-analog converters (DAC) to reproduce the analog signal after digital signal processing. · Analog pre-processing (before the ADC) and postpressing (after the DAC) are needed, such as amplification, filtering, equalization.)
Zou Zhige
RCVLSI&S
10
1.1 why Analog？(5)
Zou Zhige
RCVLSI&S
11
1.1 why Analog？(6) • Digital Communications
Zou Zhige
RCVLSI&S
12
1.1 why Analog？(7) • Digital Communications
Multi level to reduce the bandwidth Demand higher precision ADC and DAC Zou Zhige
RCVLSI&S
13
1.1 why Analog？(8) • Disk Drive Electronics
Zou Zhige
RCVLSI&S
14
1.1 why Analog？(9) • Optical Receivers
Zou Zhige
RCVLSI&S
15
1.1 why Analog？(10) • Sensors
Zou Zhige
RCVLSI&S
16
1.2 Why is analog design challenging?(1) • Digital circuits deal primarily with speed power tradeoff. • Analog circuits deal with multi-dimensional tradeoff of speed, power, gain, precision, supply, … • Due to speed and precision requirements, analog circuits are much more sensitive to noise, crosstalk, and other interferers.
Zou Zhige
RCVLSI&S
17
1.2 Why is analog design challenging?(2) • Analog circuits are much more sensitive to secondorder device effects • High performance analog circuit design can rarely be automated - typically require hand-crafted design and layout • Modeling and simulation of analog circuits is still problematic, requiring experience and intuition
Zou Zhige
RCVLSI&S
18
1.2 Why is analog design challenging?(3) • Economic forces require the development of analog circuits in mainstream digital processes • Economic forces pushing the integration of analog and digital functions onto a single substrate • Many levels of abstraction are required
Analog is needed! Zou Zhige
RCVLSI&S
19
1.3 Why CMOS Integrated Circuit? 1.3.1 Why CMOS? · Very large scale integration of both high-density digital circuits
(such as DSP and memory) and analog circuits (including amplifiers, filters, and A/D & D/A converters) for low cost. · Ideal properties of MOS switches for high accuracy sample-data circuits, such as switched-capacitor filters and A/D & D/A converters. · Device scaling : new CMOS technologies with smaller feature sizes (such as 0.25mm and 0.18mm) can operate at increasingly high speed (5GHz), comparable to some bipolar technologies.
Zou Zhige
RCVLSI&S
20
Why CMOS? (cont.) Bipolar silicon technologies · Bipolar tr. can operate at higher frequencies than CMOS with relatively smaller power consumption. · Suitable for pure analog integration with relatively high operating speed (such as RF circuits) or relatively high power (such as ADSL line drivers) applications. · Digital circuits in bipolar are power hungry, prohibiting very large scale integration. BiCMOS technologies have most advantages of both CMOS and bipolar technologies but at the expense of higher manufacturing cost due to required extra processing steps. CMOS technologies become mainstream for mixed-signal integration due to the advantages of low cost and high integration density. Zou Zhige
RCVLSI&S
21
From Bipolar to MOS transistors
Zou Zhige
RCVLSI&S
22
1.3.2 Why Integrated? A system, which consisted of a large number of integrated and discrete components, was power-hungry, huge, and expensive! Driven by primarily the memory and microprocessor market, integrated circuit technologies have also embraced analog design extensively, affording a complexity, speed, and precision that would be impossible to achieve using discrete implementations.
Zou Zhige
RCVLSI&S
23
Why Integrated? (cont.)
Zou Zhige
RCVLSI&S
24
We have answered • Why Analog ? • Why CMOS Analog ? • Why CMOS Analog Integrated ?
Zou Zhige
RCVLSI&S
25
1.4 General Concepts (1) 1.4.1 Levels of Abstraction Our method: We begin with device physics and develop increasingly more complex circuit topologies.
Abstraction levels in circuit design Zou Zhige
RCVLSI&S
26
1.4 General Concepts (2) 1.4.2 Robust Analog Design Many device and circuit parameters vary with the fabrication process, supply voltage, and ambient temperature. We denote these effects by PVT and design circuits such that their performance remains in an acceptable range of PVT variations. Robust analog design in CMOS technology is a challenging task because device parameters vary significantly from wafer to wafer.
Zou Zhige
RCVLSI&S
27
1.4 General Concepts (3) 1.4.3 Notations Definition
Quantity
Subscript
Bias(dc Value of the signal)
Uppercase
Uppercase
ID
Signal(ac Value of the signal)
Lowercase
Lowercase
id
Bias+Signal
Lowercase
Uppercase
iD
Uppercase
Lowercase
Idm
(Total instantaneous
of the signal)
Complex variable, phasor, or RMS value of the signal
Zou Zhige
Example
RCVLSI&S
28
1.4 General Concepts (4)
Notation for Signals
Zou Zhige
RCVLSI&S
29
1.4.4 Amplifier and current/voltage sources
Zou Zhige
RCVLSI&S
30
1.4.5 Small Signal Input and Output Impedances • Calculations of Small Signal Input and Output Impedances How to calculate input and output impedances (or admittances) of an amplifier? In the following sections, we assume that the amplifier is a voltage amplifier, whose input and output are both voltages. But we can easily extend the principles to any other types of amplifiers, such as current amplifiers (input and output are both currents), transimpedance amplifiers (input: current, output: voltage), and transconductance amplifiers (input: voltage, output: current).
Zou Zhige
RCVLSI&S
31
Small Signal Input and Output Impedances (cont.) 1) Input impedance
i) Apply vtst at the input (* see note below), draw the small signal diagram. ii) Calculate itst = f (vtst) , or vtst = f (itst) iii) The input impedance is given by zin = vtst / its and the input admittance is yin = itst / vtst * Note: If the amplifier requires an output termination, we should terminate the output accordingly. The load condition may affect the input impedance. Zou Zhige
RCVLSI&S
32
Small Signal Input and Output Impedances (cont.) 2) Output impedance
i) Set vin=0 , or if the input is a signal current, set iin= 0 (** see note below). ii) Apply vtst at the output, draw the small signal diagram. iii) Calculate itst = f (vtst) or vtst = f (itst) iv) The output impedance is given by zout = vtst / itst and the output admittance yout = itst /vtst ** Note: If the amplifier requires some input termination, we should terminate the input accordingly. The input termination may affect the output impedance. Zou Zhige
RCVLSI&S
33
1.4.6 Analysis and Design
Analysis and design processes
Zou Zhige
RCVLSI&S
34
Chap 1 Summary • Introduction to Analog Design • CMOS technology and device models • Single-stage amplifiers • Differential pairs • Current sources and mirrors, active loads • Frequency Response of Amplifiers
Zou Zhige
RCVLSI&S
35
Information •
Required text — Razavi《Design of Analog CMOS Integrated Circuits》
•
Reference — Gray《Analysis and Design of Analog Integrated Circuits, 4th》 — Hspice Handbook（Please download from http://icc.hust.edu.cn）
•
Assignments — Lecture 32 hours，Project design 8 hours
•
Course Grade Composition — Homework 10％，Design Project 20％，Final Exam 70％
•
Question — Please Email to [email protected] , or phone 13377878863 — Assistant: 高专 (13297967279), Email: [email protected] Zou Zhige
RCVLSI&S
2
Circuit Simulation • Primary tools: HSpice/AWaves • Course Technology – 0.35μm CMOS –Spice model is provided at http://icc.hust.edu.cn • Caution — Spice is nothing but a "calculator" that lets you evaluate and test your ideas — There is no need to simulate anything unless you already know the (approximate) answer!
Zou Zhige
RCVLSI&S
3
Course Topics • Introduction to Analog Design • CMOS technology and device models • Single-stage amplifiers • Differential pairs • Current sources and mirrors, active loads • Frequency Response of Amplifiers
Zou Zhige
RCVLSI&S
4
Overview • Reading – Chapter 1 (p1-8) •
Introduction – In this first lecture, we will introduce “Why CMOS Analog Integrated Circuit?” and “General Concepts in Analog Design.”
Zou Zhige
RCVLSI&S
5
1.1 why Analog？(1) 1.1.1 Analog signals versus Digital signals: • Signal: A signal will be considered to be any detectable value of voltage, current, or charge. A signal should convey information about the state or behavior of a physical system. • Analog signal is a signal that is defined over a continuous range of time and a continuous range of amplitudes. • Digital signal is a signal that is defined only at discrete values of amplitude, or said another way, a digital signal is quantized to discrete values. Zou Zhige
RCVLSI&S
6
1.1 why Analog？(2) Advantages of Digital signal processing compared with analog signal processing: – Robustness: digital signal processing is insensitive to process variations, supply voltage change, temperature variation, interference, and aging; – Programmability: digital signal processing algorithms can be changed fairly easily by changing the coefficients or the software codes; – Flexibility: some signal processing algorithms have extra degree of freedom if implemented in digital, such as linear phase filter. Zou Zhige
RCVLSI&S
7
1.1 why Analog？(3) Digital System Exist Today: – Digital Mobil Phone; – Digital Film; – Digital TV; – Digital Power Amplifier; – Digital filter; – Digital ……
Almost every thing is Digital . So, Analog is out of date? Zou Zhige
RCVLSI&S
8
1.1 why Analog？(3) 1.1.2 why Analog？ As many applications have moved to digital domain, analog circuits seem obsolete. But actually analog circuit designers are in strong demand today. Why?!!! The physical world is in analog (at macroscopic level), such as · The output signals of many signal sources are all in analog form; · The RF signals in space and at the antenna are also in analog.
Zou Zhige
RCVLSI&S
9
1.1 why Analog？(4) We need · Analog-to-digital converters (ADC) to digitize the input signal, · Digital-to-analog converters (DAC) to reproduce the analog signal after digital signal processing. · Analog pre-processing (before the ADC) and postpressing (after the DAC) are needed, such as amplification, filtering, equalization.)
Zou Zhige
RCVLSI&S
10
1.1 why Analog？(5)
Zou Zhige
RCVLSI&S
11
1.1 why Analog？(6) • Digital Communications
Zou Zhige
RCVLSI&S
12
1.1 why Analog？(7) • Digital Communications
Multi level to reduce the bandwidth Demand higher precision ADC and DAC Zou Zhige
RCVLSI&S
13
1.1 why Analog？(8) • Disk Drive Electronics
Zou Zhige
RCVLSI&S
14
1.1 why Analog？(9) • Optical Receivers
Zou Zhige
RCVLSI&S
15
1.1 why Analog？(10) • Sensors
Zou Zhige
RCVLSI&S
16
1.2 Why is analog design challenging?(1) • Digital circuits deal primarily with speed power tradeoff. • Analog circuits deal with multi-dimensional tradeoff of speed, power, gain, precision, supply, … • Due to speed and precision requirements, analog circuits are much more sensitive to noise, crosstalk, and other interferers.
Zou Zhige
RCVLSI&S
17
1.2 Why is analog design challenging?(2) • Analog circuits are much more sensitive to secondorder device effects • High performance analog circuit design can rarely be automated - typically require hand-crafted design and layout • Modeling and simulation of analog circuits is still problematic, requiring experience and intuition
Zou Zhige
RCVLSI&S
18
1.2 Why is analog design challenging?(3) • Economic forces require the development of analog circuits in mainstream digital processes • Economic forces pushing the integration of analog and digital functions onto a single substrate • Many levels of abstraction are required
Analog is needed! Zou Zhige
RCVLSI&S
19
1.3 Why CMOS Integrated Circuit? 1.3.1 Why CMOS? · Very large scale integration of both high-density digital circuits
(such as DSP and memory) and analog circuits (including amplifiers, filters, and A/D & D/A converters) for low cost. · Ideal properties of MOS switches for high accuracy sample-data circuits, such as switched-capacitor filters and A/D & D/A converters. · Device scaling : new CMOS technologies with smaller feature sizes (such as 0.25mm and 0.18mm) can operate at increasingly high speed (5GHz), comparable to some bipolar technologies.
Zou Zhige
RCVLSI&S
20
Why CMOS? (cont.) Bipolar silicon technologies · Bipolar tr. can operate at higher frequencies than CMOS with relatively smaller power consumption. · Suitable for pure analog integration with relatively high operating speed (such as RF circuits) or relatively high power (such as ADSL line drivers) applications. · Digital circuits in bipolar are power hungry, prohibiting very large scale integration. BiCMOS technologies have most advantages of both CMOS and bipolar technologies but at the expense of higher manufacturing cost due to required extra processing steps. CMOS technologies become mainstream for mixed-signal integration due to the advantages of low cost and high integration density. Zou Zhige
RCVLSI&S
21
From Bipolar to MOS transistors
Zou Zhige
RCVLSI&S
22
1.3.2 Why Integrated? A system, which consisted of a large number of integrated and discrete components, was power-hungry, huge, and expensive! Driven by primarily the memory and microprocessor market, integrated circuit technologies have also embraced analog design extensively, affording a complexity, speed, and precision that would be impossible to achieve using discrete implementations.
Zou Zhige
RCVLSI&S
23
Why Integrated? (cont.)
Zou Zhige
RCVLSI&S
24
We have answered • Why Analog ? • Why CMOS Analog ? • Why CMOS Analog Integrated ?
Zou Zhige
RCVLSI&S
25
1.4 General Concepts (1) 1.4.1 Levels of Abstraction Our method: We begin with device physics and develop increasingly more complex circuit topologies.
Abstraction levels in circuit design Zou Zhige
RCVLSI&S
26
1.4 General Concepts (2) 1.4.2 Robust Analog Design Many device and circuit parameters vary with the fabrication process, supply voltage, and ambient temperature. We denote these effects by PVT and design circuits such that their performance remains in an acceptable range of PVT variations. Robust analog design in CMOS technology is a challenging task because device parameters vary significantly from wafer to wafer.
Zou Zhige
RCVLSI&S
27
1.4 General Concepts (3) 1.4.3 Notations Definition
Quantity
Subscript
Bias(dc Value of the signal)
Uppercase
Uppercase
ID
Signal(ac Value of the signal)
Lowercase
Lowercase
id
Bias+Signal
Lowercase
Uppercase
iD
Uppercase
Lowercase
Idm
(Total instantaneous
of the signal)
Complex variable, phasor, or RMS value of the signal
Zou Zhige
Example
RCVLSI&S
28
1.4 General Concepts (4)
Notation for Signals
Zou Zhige
RCVLSI&S
29
1.4.4 Amplifier and current/voltage sources
Zou Zhige
RCVLSI&S
30
1.4.5 Small Signal Input and Output Impedances • Calculations of Small Signal Input and Output Impedances How to calculate input and output impedances (or admittances) of an amplifier? In the following sections, we assume that the amplifier is a voltage amplifier, whose input and output are both voltages. But we can easily extend the principles to any other types of amplifiers, such as current amplifiers (input and output are both currents), transimpedance amplifiers (input: current, output: voltage), and transconductance amplifiers (input: voltage, output: current).
Zou Zhige
RCVLSI&S
31
Small Signal Input and Output Impedances (cont.) 1) Input impedance
i) Apply vtst at the input (* see note below), draw the small signal diagram. ii) Calculate itst = f (vtst) , or vtst = f (itst) iii) The input impedance is given by zin = vtst / its and the input admittance is yin = itst / vtst * Note: If the amplifier requires an output termination, we should terminate the output accordingly. The load condition may affect the input impedance. Zou Zhige
RCVLSI&S
32
Small Signal Input and Output Impedances (cont.) 2) Output impedance
i) Set vin=0 , or if the input is a signal current, set iin= 0 (** see note below). ii) Apply vtst at the output, draw the small signal diagram. iii) Calculate itst = f (vtst) or vtst = f (itst) iv) The output impedance is given by zout = vtst / itst and the output admittance yout = itst /vtst ** Note: If the amplifier requires some input termination, we should terminate the input accordingly. The input termination may affect the output impedance. Zou Zhige
RCVLSI&S
33
1.4.6 Analysis and Design
Analysis and design processes
Zou Zhige
RCVLSI&S
34
Chap 1 Summary • Introduction to Analog Design • CMOS technology and device models • Single-stage amplifiers • Differential pairs • Current sources and mirrors, active loads • Frequency Response of Amplifiers
Zou Zhige
RCVLSI&S
35
