EE 230 Lecture 27. Nonlinear Circuits and Nonlinear Devices. Diode BJT MOSFET

Transcription

1 EE 23 Lecture 27 Nonlinear Circuits an Nonlinear evices ioe BJT MOSFET

2 eview from Last Time: Wein-Brige Oscillator Noninverting Amplifier 1 2 OUT K o ω OSC 1 C C C C Feeback Network Nonlinearity of Noninverting Amplifier Limits Amplitue of OUT an when saturation occurs, will cause istortion

3 eview from Last Time: Wein-Brige Oscillator Noninverting Amplifier 1 2 OUT K o OUT SATH C C N C Feeback Network Gain (slope)=3+ε SATL Nonlinearity of Noninverting Amplifier

4 eview from Last Time: Amplifiers with less abrupt change in slope will reuce istortion OUT SATH N Gain (slope)=3 SATL

5 eview from Last Time: Amplifiers with less abrupt change in slope 2 3 SATH OUT 1 OUT N Gain (slope)=3 N SATL N γ N γ = 1+ - < < OUT N γ N γ N γ N γ 1 3

6 eview from Last Time: Wein-Brige Oscillator with Low istortion Amplitue Limiting Noninverting Amplifier OUT C C C Feeback Network

7 Observation: Nonlinear evices Have Provie ery Useful Performance Capabilities Not Obtainable with Linear Circuits OUT N XX

8 The Electronics Worl as We See t Until Now Linear Circuits Nonlinear Circuits esistive Networks Amplifiers (epenent Sources) X A Nonlinear evice C X Passive Filters (LC Networks) Active Filters Comparators Waveform Generators Sensor nterfaces Nonlinear Amplifiers Analog to igital Converters (AC) igital to Analog Converters (AC)

9 The Electronics Worl as We See t Until Now Linear Circuits Nonlinear Circuits X esistive Networks Amplifiers (epenent Sources) X A Nonlinear evice C Passive Filters (LC Networks) Active Filters Comparators Waveform Generators Sensor nterfaces Nonlinear Amplifiers Analog to igital Converters (AC) igital to Analog Converters (AC) Unesire Nonlinear Behavior

10 The Electronics Worl as We See t Until Now Perception: Most of the Electronics Worl s Linear A few Useful Nonlinear Applications Nonlinear Analysis is Har

11 The eal Electronics Worl Linear Circuits Nonlinear Circuits X esistive Networks X A Nonlinear evice C G GS G S Nonlinear evice S S Passive Filters (LC Networks) All Logic Circuits Comparators Nonlinear Amplifiers Linearize Nonlinear Circuits (small signal moel) Amplifiers (epenent Sources) Analog to igital Converters (AC) Sensor Active nterfaces Filters Waveform Generators igital to Analog Converters (AC) Waveform Generators

12 The eal Electronics Worl Linear Circuits Nonlinear Circuits esistive Networks MOSFET ioe BJT Passive Filters (LC Networks) All Logic Circuits Comparators Nonlinear Amplifiers Linearize Nonlinear Circuits (small signal moel) Amplifiers (epenent Sources) Analog to igital Converters (AC) Sensor Active nterfaces Filters Waveform Generators igital to Analog Converters (AC) Waveform Generators

13 The eal Electronics Worl Perception: Most of the Electronics Worl s Linear A few Useful Nonlinear Applications Nonlinear Analysis is Har eality: Most Electronic Circuits are Nonlinear Many combine nonlinear evices to make nearly linear circuits Nonlinear Analysis is ifferent Sometimes Easier than Linear Analysis Sometimes Harer than Linear Analysis But mostly just ifferent

14 The eal Electronics Worl Linear Circuits Nonlinear Circuits esistive Networks MOSFET ioe BJT Passive Filters (LC Networks) All Logic Circuits Comparators Nonlinear Amplifiers Linearize Nonlinear Circuits (small signal moel) Amplifiers (epenent Sources) Analog to igital Converters (AC) Sensor Active nterfaces Filters Waveform Generators igital to Analog Converters (AC) Waveform Generators

15 Basic Nonlinear evices MOSFET ioe BJT X G GS G S Nonlinear evice S S X A Nonlinear evice C = G <1 = 1-1- GS >1, < -1 GS S GS -4 S S GS -1 GS >1, S > GS GS if if

16 Basic Nonlinear evices MOSFET ioe BJT Propose in approx 193 Manufacture in approx 197 ominant evice in igital Cs toay Wiely use for analog Cs evice upon which semiconuctor inustry toay is base Propose an manufacture in approx 194 Physics unerstoo approx 1948 Wiely use in power applications Some use in signal processing an instrumentation Available in most semiconuctor processes without aitional cost but often not optimize nvente in 1948 an manufacture almost immeiately thereafter ominant evice in semiconuctor inustry till mi 7s Preferre in many linear Cs Offers some spee benefits over MOSFET Goo BJTs available in some niche processes

17 The ioe Anoe Anoe Cathoe p-type n-type Cathoe

18 Types of ioes pn junction ioes Signal or ectifier Pin or Photo Light Emitting LE Laser ioe Metal-semiconuctor junction ioes Zener aractor or aricap Schottky Barrier

19 The eal ioe if if

20 The eal ioe if if OFF ON ON OFF ali for >

21 Consier a simple ioe circuit OUT ON OFF N > Analysis: Case 1 N Guess ioe in ON OUT solution: OUT = N vali for: > = OUT N = Always express in terms of N N >

22 Consier a simple ioe circuit OUT ON OFF N > Analysis: Case 2 N Guess ioe is OFF OUT solution: OUT = vali for: = = N OUT N N

23 Consier a simple ioe circuit OUT N > N N = OUT N OUT N

24 Consier a simple ioe circuit OUT OUT N N f N = M sinωt N t OUT t Serves as a rectifier very useful function!

25 (amps) - characteristics of pn junction (signal or rectifier ioe) ioe Characteristics (volts)

26 (amps) - characteristics of pn junction (signal or rectifier ioe).1.8 ioe Characteristics (volts) S e t 1 S is a constant (typically 1fA < S t =kt/q 1fA) k Boltzman s Constant, q charge of electron, T temp in K k/q=8.63e-5 / K At room temperature, t is approximately 25m highly temperature epenent (wiely use in temp sensors!)

27 (amps) - characteristics of pn junction (signal or rectifier ioe).1 ioe Characteristics (volts) Terme ioe Equation S e t 1 Uner reverse bias, Uner forwar bias, S S e t ioe Equation or forwar bias simplification is unwiely to work with analytically

28 Consier again the basic rectifier circuit OUT N N OUT S e t 1 OUT S e N t OUT 1 Even the simplest ioe circuit oes not have a close-form solution when ioe equation is use to moel the ioe!! ue to the nonlinear nature of the ioe equation Simplifications are essential if analytical results are to be obtaine

29 (amps) Lets stuy the ioe equation a little further t S e 1 ioe Characteristics (volts) Power issipation Becomes estructive if >.85 (actually less)

30 (amps) Lets stuy the ioe equation a little further t S e 1 ioe Characteristics E-6 1E-8 1E-1 1E (volts) For two ecaes of current change, is close to.6 This is the most useful current range for many applications

31 (amps) Lets stuy the ioe equation a little further t S e 1 ioe Characteristics (volts) For two ecaes of current change, is close to.6 This is the most useful current range for many applications

32 (amps) Lets stuy the ioe equation a little further S e t 1 ioe Characteristics (volts) Wiely Use Piecewise Linear Moel

33 (amps) Lets stuy the ioe equation a little further t S e 1 ioe Characteristics (volts).6.6

34 Lets stuy the ioe equation a little further t S e 1 Piecewise Linear Moel.6.6 Equivalent Circuit A C A C Off State A C.6 On State

35 (amps) Lets stuy the ioe equation a little further t S e 1 ioe Characteristics (volts) Slightly More Accurate Piecewise Linear Moel

36 (amps) Lets stuy the ioe equation a little further t S e 1 ioe Characteristics (volts).6.6

37 Lets stuy the ioe equation a little further t S e 1 Piecewise Linear Moel with ioe esistance.6.6 ( is rather small: often in the 2Ώ to 1Ώ range): Equivalent Circuit A C A C Off State A C.6 On State

38 Consier again the basic rectifier circuit OUT N Analyze with piecewise linear moel Case 1 =.6.6 OUT OUT = N vali for.6 but = N vali for N.6

39 Consier again the basic rectifier circuit OUT N Analyze with piecewise linear moel.6.6 Case 2 =.6 OUT = N -.6 N.6 OUT vali for > -.6 N but = vali for N >.6

40 Consier again the basic rectifier circuit OUT N Analyze with piecewise linear moel Solution summary:.6 N = OUT N -.6 N >.6 OUT 1 1 N.6