l10_analog_building_block

l10_analog_building_block - L10: Analog Building Blocks...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
L10: 6.111 Spring 2007 1 Introductory Digital Systems Laboratory L10: Analog Building Blocks L10: Analog Building Blocks ( ( OpAmps OpAmps , A/D, D/A) , A/D, D/A) Acknowledgement: Dave Wentzloff
Background image of page 1

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

View Full DocumentRight Arrow Icon
L10: 6.111 Spring 2007 2 Introductory Digital Systems Laboratory Introduction to Operational Amplifiers Introduction to Operational Amplifiers DC Model ± Typically very high input resistance ~ 300K ± High DC gain (~10 5 ) ± Output resistance ~75 id v a id v in R out R + out v in out V f a V = ) ( a(f) f 10Hz 10 5 -20dB/ decade LM741 Pinout +10 to +15V -10 to -15V
Background image of page 2
L10: 6.111 Spring 2007 3 Introductory Digital Systems Laboratory The Inside of a 741 The Inside of a 741 OpAmp OpAmp Differential Input Stage Additional Gain Stage Output Stage Current Source for biasing Bipolar version has small input Bias current MOS OpAmps have ~ 0 input current Gain is Sensitive to Operating Condition (e.g., Device, Temperature, Power supply voltage, etc.) Output devices provides large drive current
Background image of page 3

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

View Full DocumentRight Arrow Icon
L10: 6.111 Spring 2007 4 Introductory Digital Systems Laboratory Simple Model for an Simple Model for an OpAmp OpAmp + - i + ~ 0 i - ~ 0 + - + - v id v out v out v id V CC = 10V -V CC = -10V ε = 100 µ V -100 µ V Reasonable approximation + - v id + - av id + - v out Linear Mode If -V CC < v out < V CC + - v id -V CC + - v out Negative Saturation v id < - ε - + + - v id + - v out Positive Saturation v id > ε - + +V CC -V CC V CC Small input range for “Open” loop Configuration
Background image of page 4
L10: 6.111 Spring 2007 5 Introductory Digital Systems Laboratory The Power of (Negative) Feedback The Power of (Negative) Feedback - + v id + - av id + - v out in v R 2 - + R 1 1 R 2 R - + + - out v in v 0 2 1 = + + + R v v R v v id out id in + + = 2 2 1 1 1 1 R R a R a v R v out in a v v out id = () 1 1 1 2 2 1 2 >> + + = a if R R R R a a R v v in out ± Overall (closed loop) gain does not depend on open loop gain ± Trade gain for robustness ± Easier analysis approach: “virtual short circuit approach” ± v + = v - = 0 if OpAmp is linear
Background image of page 5

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

View Full DocumentRight Arrow Icon
L10: 6.111 Spring 2007 6 Introductory Digital Systems Laboratory Basic Basic OpAmp OpAmp Circuits Circuits Non-inverting Voltage Follower (buffer) + in v in out v v + - out v in out v R R R v 1 2 1 + Differential Input Integrator dt v v t in RC out 1 () 1 2 1 2 in in R R out v v v
Background image of page 6
L10: 6.111 Spring 2007 7 Introductory Digital Systems Laboratory Use With Open Loop Use With Open Loop Analog Comparator: Is V+ > V- ? The Output is a DIGITAL signal LM311 is a single supply comparator
Background image of page 7

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

View Full DocumentRight Arrow Icon
L10: 6.111 Spring 2007 8 Introductory Digital Systems Laboratory Data Conversion: Quantization Noise Data Conversion: Quantization Noise A/D Conversion D/A Conversion 00 01 10 11 0 4 ref V 2 ref V 4 3 ref V Binary code An al og O ut put 00 01 10 11 0 4 ref V 2 ref V 4 3 ref V Analog Input Bi na ry Ou tp ref V ± Quantization noise exists even with ideal A/D and D/A converters noise v LSB A/D D/A digital code in v Quantization noise + 4 ref V 2 ref V 4 3 ref V ref V in v
Background image of page 8
L10: 6.111 Spring 2007 9 Introductory Digital Systems Laboratory Non
Background image of page 9

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

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 08/23/2009 for the course EECS 6.111 taught by Professor Prof.ananthachandrakasan during the Spring '04 term at MIT.

Page1 / 28

l10_analog_building_block - L10: Analog Building Blocks...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online