MIT6_012F09_lec24 - 6.012 Microelectronic Devices and...

Info icon This preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
6.012 - Microelectronic Devices and Circuits Lecture 24 - Intrin. Freq. Limits - Outline Announcements Final Exam - Tuesday, Dec 15, 9:00 am - 12 noon Review - Shunt feedback capacitances: C µ and C gd Miller effect: any C bridging a gain stage looks bigger at the input Marvelous cascode: CE/S-CB/G (E/SF-CB/G work, too - see µ A741 ) large bandwidth, large output resistance used in gain stages and in current sources Using the Miller effect to advantage: Stabilizing OP Amps - the µ A741 Intrinsic high frequency limitations of transistors General approach MOSFETs: f T biasing for speed impact of velocity saturation design lessons BJTs: f β , f T , f α biasing for speed design lessons Clif Fonstad, 12/8/09 Lecture 24 - Slide 1
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Summary of OCTC and SCTC results OCTC: an estimate for ω HI log ! log |A vd | ! b ! c ! d ! a ! LO ! LO * ! 4 ! 5 ! 2 ! 1 ! 3 ! HI * ! HI Mid-band Range 1. ω H I * is a weighted sum of ω 's associated with device capacitances: (add RC's and invert) 2. Smallest ω (largest RC) dominates ω HI * 3. Provides a lower bound on ω HI SCTC: an estimate for ω LO 1. ω LO * is a weighted sum of w's associated with bias capacitors: (add ω 's directly) 2. Largest ω (smallest RC) dominates ω LO * 3. Provides a upper bound on ω LO Clif Fonstad, 12/8/09 Lecture 24 - Slide 2
Image of page 2
The Miller effect (general) + - v in (1-A v )v in C m v out = A v v in + - + - i in Consider an amplifier shunted by a capacitor, and consider how the capacitor looks at the input and output terminals: Note: A v is negative v out + - C m v in + - A v i in = C m d 1 " A v ( ) v in [ ] dt = 1 " A v ( ) C m dv in dt + - v out C m + - v in (1-A v )C m C in looks much C m 1 " A v ( ) A v # C m bigger than C m C out looks like C m Clif Fonstad, 12/8/09 Lecture 24 - Slide 3
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
The cascode when the substrate is grounded: High frequency issues: L.E.C. of cascode: can't use equivalent transistor idea here because it didn't address the issue of the C's! r o2 v gs1 g m1 v gs1 r o1 + - (g m2 +g mb2 )v gs2 + - v gs2 + - v out r l C db1 +C gs2 +C bs2 C gd2 +C bd2 C gd1 C gs1 g 1 d 1 ,s 2 ,b 2 d 2 s 1 ,b 1 ,b 2 s 1 ,b 1 ,g 2 ,b 2 g 2 ,b 2 Voltage gain -1 so Voltage gain g r l , m minimal Miller effect. without Miller effect. Common-source gain without the Miller effect penalty! Clif Fonstad, 12/8/09 Lecture 24 - Slide 4
Image of page 4
Multi-stage amplifier analysis and design: The µ A741 Figuring the circuit out: Emitter-follower/ Current mirror load Simplified schematic Push-pull output common-base "cascode" differential gain stage EF CB The full schematic © Source unknown. All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse . Darlington common- emitter gain stage © Source unknown. All rights reserved. Clif Fonstad, 12/8/09 This content is excluded from our Creative Commons license. Lecture 24 - Slide 5 For more information, see http://ocw.mit.edu/fairuse .
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Multi-stage amplifier analysis and design: Understanding the µ A741 input "cascode" Begin with the BJT building-block stages: + - v out v t + - r t i out i in g m v !
Image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.
  • Fall '09
  • CharlesG.Sodini
  • Electronic amplifier, Cascode, Common source, Common emitter, Clif Fonstad, short-circuit current gain

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern