Tài liệu Circuits & Electronics P9 doc

6.002 Fall 2000 Lecture 1 9 6.002 CIRCUITS AND ELECTRONICS MOSFET Amplifier Large Signal Analysis 6.002 Fall 2000 Lecture 2 9  Amp constructed using dependent source  Superposition with dependent sources: one way tleave all dependent sources in; solve for one independent source at a time [section 3.5.1 of the text]  Next, quick review of amp … Reading: Chapter 7.3–7.7 + – + – a ′ a v b ′ b )(vfi =  a ′ a b ′ b control port DS output port Dependent source in a circuit Review 6.002 Fall 2000 Lecture 3 9 Amp review LDSO RiVv −= () 2 I 1v 2 K − for v I ≥ 1V = 0 otherwise S V O v L R + – () 2 ID 1v 2 K i −= I v VCCS 6.002 Fall 2000 Lecture 4 9 Key device Needed: Let’s look at our old friend, the MOSFET … A B v C ( ) vfi = voltage controlled current source 6.002 Fall 2000 Lecture 5 9 Key device Needed: Our old friend, the MOSFET … First, we sort of lied. The on-state behavior of the MOSFET is quite a bit more complex than either the ideal switch or the resistor model would have you believe. D S G D S TGS Vv < G TGS Vv ≥ ? 6.002 Fall 2000 Lecture 6 9 Graphically DS v DS i TGS Vv ≥ TGS Vv < TGS Vv ≥ 1GS v Saturation region T r i o d e re g i o n S MODEL DS v DS i SR MODEL DS v DS i Demo TGS Vv < TGS Vv < 2GS v 3GS v + – DS v + – DS i GS v . TGSDS Vvv −= Cutoff region 6.002 Fall 2000 Lecture 7 9 Graphically DS v DS i TGS Vv ≥ TGS Vv < TGS Vv ≥ 1GS v Saturation region T r i o d e re g i o n S MODEL DS v DS i SR MODEL DS v DS i TGS Vv < TGS Vv < 2GS v 3GS v + – DS v + – DS i GS v . TGSDS Vvv −= Notice that MOSFET behaves like a current source when TGSDS Vvv −≥ 6.002 Fall 2000 Lecture 8 9 MOSFET SCS Model D S G D S TGS Vv < G () 2 2 TGS Vv K −= when TGSDS Vvv −≥ () GSDS vfi = TGS Vv ≥ D S G When the MOSFET is in its saturation region, and the switch current source (SCS) model of the MOSFET is more accurate than the S or SR model TGSDS Vvv −≥ 6.002 Fall 2000 Lecture 9 9 Reconciling the models… TGSDS Vvv −≥ TGSDS Vvv −< use SCS model use SR model Note: alternatively (in more advanced courses) or, use SU Model (Section 7.8 of A&L) S MODEL SR MODEL SCS MODEL for fun! for digital designs for analog designs When to use each model in 6.002? DS v DS i TGS Vv ≥ TGS Vv < TGS Vv ≥ 1GS v Saturation region T r i o d e re g i o n DS v DS i DS v DS i TGS Vv < TGS Vv < 2GS v 3GS v . TGSDS Vvv −= 6.002 Fall 2000 Lecture 10 9 Back to Amplifier in saturation region I v O v AMP S V S V L R I v O v G D S () 2 2 TIDS Vv K i −= To ensure the MOSFET operates as a VCCS, we must operate it in its saturation region only. To do so, we promise to adhere to the “saturation discipline” . < TGS Vv < 2GS v 3GS v + – DS v + – DS i GS v . TGSDS Vvv −= Cutoff region 6.002 Fall 2000 Lecture 7 9 Graphically DS v DS i TGS Vv ≥ TGS Vv <. DS v DS i TGS Vv ≥ TGS Vv < TGS Vv ≥ 1GS v Saturation region T r i o d e re g i o n DS v DS i DS v DS i TGS Vv < TGS Vv < 2GS v 3GS v . TGSDS