Tài liệu Circuits & Electronics P11 pdf

6.002 Fall 2000 Lecture 1 11 6.002 CIRCUITS AND ELECTRONICS Small Signal Circuits 6.002 Fall 2000 Lecture 2 11  Small signal notation  v A = V A + v a total operating point small signal () i Vv I I out IOUT vvf dv d v v fv II ⋅= = = )(  S V L R oOO vVv += I V + – + – iII vVv += i v Review: 6.002 Fall 2000 Lecture 3 11 I Graphical view (using transfer function) behaves linear for small perturbations I v O v Review: 6.002 Fall 2000 Lecture 4 11 II Mathematical view () L TI SO R VvK Vv 2 2 − −= () i Vv LTIS I o v RVv K V dv d v II ⋅       −− = = 2 2 related to V I constant for fixed DC bias () iLTIo vRVVKv ⋅−−= g m Review: 6.002 Fall 2000 Lecture 5 11 Demo Choosing a bias point: DS i O v L SL TI KR VKR Vv 211 ++− += TI Vv = 2 ODS v 2 K i < load line L O L S DS R v R V i −= How to choose the bias point, using yet another graphical view based on the load line O V I V input signal response ILm VRg ∝ 1. Gain 2. Input valid operating range for amp. 3. Bias to select gain and input swing. 6.002 Fall 2000 Lecture 6 11 III The Small Signal Circuit View We can derive small circuit equivalent models for our devices, and thereby conduct small signal analysis directly on circuits () 2 TID Vv 2 K i −= + – R OUT v V S + – I v 1 e.g. large signal circuit model for amp We can replace large signal models with small signal circuit models. Foundations: Section 8.2.1 and also in the last slide in this lecture. 6.002 Fall 2000 Lecture 7 11 Small Signal Circuit Analysis 1 Find operating point using DC bias inputs using large signal model. Develop small signal (linearized) models for elements. Replace original elements with small signal models. 2 3 Analyze resulting linearized circuit… Key: Can use superposition and other linear circuit tools with linearized circuit! 6.002 Fall 2000 Lecture 8 11 Small Signal Models MOSFET A large signal () 2 2 TGSDS Vv K i −= D S GS v Small signal? 6.002 Fall 2000 Lecture 9 11 Small Signal Models MOSFET A large signal () 2 2 TGSDS Vv K i −= D S GS v Small signal: small signal D S gs v ( ) gsTGSds vVVKi −= gsmds vgi = () 2 2 TGSDS Vv K i −= () gs Vv TGS GS ds vVv K v i GSGS ⋅       − ∂ ∂ = = 2 2 () gsTGSds vVVKi ⋅−= g m i ds is linear in v gs ! 6.002 Fall 2000 Lecture 10 11 DC Supply V S B large signal SS Vv = s Ii S S s i i V v SS ⋅ ∂ ∂ = = 0v s = + – SS Vv = S i + – s v s i DC source behaves as short to small signals. Small signal [...]... parameters of a circuit, we can replace large signal device models with corresponding small signal device models, and then analyze the resulting small signal circuit Foundations: (Also see section 8.2.1 of A&L) KVL, KCL applied to some circuit C yields: + vA + + vOUT + + vB + 1 Replace total variables with operating point variables plus small signal variables + VA + v a + VOUT + vout + VB + vb + Operating . equations BOUTA VVV ++++ """ so, we can cancel them out BOUTA vvv ++++++ """" 1 bouta vvv ++++ """ Leaving 2. section 8.2.1 of A&L) KVL, KCL applied to some circuit C yields: III The Small Signal Circuit View bBoutOUTaA vVvVvV +++++++ """ Replace