More Non-Ideal Properties Bias Current Offset Voltage Saturation Applications of saturation.

Slides:



Advertisements
Similar presentations
Multi-stage Amplifiers
Advertisements

1.6 Op-Amp Basics High input impedance Low output impedance Made using difference amplifiers having 2 inputs and at least 1 output 1 Note: Terminals for.
Operational Amplifiers
Operational Amplifiers 1. Copyright  2004 by Oxford University Press, Inc. Microelectronic Circuits - Fifth Edition Sedra/Smith2 Figure 2.1 Circuit symbol.
Chapter 7 Operational-Amplifier and its Applications
Describe and analyze the operation of several types of comparator circuits. Describe and analyze the operation of several types of summing amplifiers.
Figure 1.17 Model of an electronic amplifier, including input resistance Ri and output resistance Ro. © 2000 Prentice Hall Inc.
Operational Amplifiers
Non-Ideal Characteristics Input impedance Output impedance Frequency response Slew rate Saturation Bias current Offset voltage.
Operational amplifier
Lecture 91 Loop Analysis (3.2) Circuits with Op-Amps (3.3) Prof. Phillips February 19, 2003.
Comparator circuits An ideal comparator compares two input voltages and produces a logic output signal whose value (high or low) depends on which of the.
Oscillators With the addition of a capacitor and resistor, the Schmitt trigger can be turned into a simple oscillator. Technically, it’s known as an astable.
Practical Differential Amplifier Design We’ve discussed Large signal behaviour Small signal voltage gain Today: Input impedance Output impedance Coupling.
Review of Linear Op-Amp Circuits We will quickly review the analysis & design of linear op-amp circuits that use negative feedback: Non-inverting amplifier.
Op Amps Lecture 30.
Coming Soon… Week 5 Tuesday (today!)TC WednesdayPAC Weeks 6 & 7 TuesdayPAC WednesdayTC Week 8- TuesdayPAC WednesdayPAC.
Department of Information Engineering357 Operation amplifier The tail, large impedance gives high CMRR Mirror as active load. High gain Follower as buffer.
Operational Amplifiers
1 ECE 3336 Introduction to Circuits & Electronics MORE on Operational Amplifiers Spring 2015, TUE&TH 5:30-7:00 pm Dr. Wanda Wosik Set #14.
Copyright © 2013 The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 Chapter 6 The Operational Amplifier.
EE2B1 Revision Points What should you be expected to do in a typical exam question ? Understanding of basic principles. Ability to perform simple circuit.
Worked Examples Practical Op-Amp Design Schmitt Trigger
Astable multivibrators I
ELECTRICAL ENGINEERING: PRINCIPLES AND APPLICATIONS, Third Edition, by Allan R. Hambley, ©2005 Pearson Education, Inc. Chapter 14 Operational Amplifiers.
Electronic Devices Ninth Edition Floyd Chapter 13.
ELECTRICA L ENGINEERING Principles and Applications SECOND EDITION ALLAN R. HAMBLEY ©2002 Prentice-Hall, Inc. Chapter 14 Operational Amplifiers Chapter.
Analogue Electronics II EMT 212/4
EKT314/4 Electronic Instrumentation
Chapter 8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Announcements Assignment 5 due tomorrow (or now)
Differential Amplifier
CHAPTER 11 Op-Amp Applications. Objectives Describe and Analyze: Audio mixers Integrators Differentiators Peak detectors Comparators Other applications.
Announcements mid-term Thursday (Oct 27 th ) Project ideas to me by Nov 1 st latest Assignment 4 due tomorrow (or now) Assignment 5 posted, due Friday.
Electronic Troubleshooting Chapter 8 Operational Amplifiers.
Microelectronic Circuits, Sixth Edition Sedra/Smith Copyright © 2010 by Oxford University Press, Inc. C H A P T E R 02 Operational Amplifiers.
10/11/2015 Operational Amplifier Characterization Chapter 3.
Module 4 Operational Amplifier
Dynamic Presentation of Key Concepts Module 5 – Part 1 Fundamentals of Operational Amplifiers Filename: DPKC_Mod05_Part01.ppt.
Electronics Principles & Applications Fifth Edition Chapter 6 Introduction to Small-Signal Amplifiers ©1999 Glencoe/McGraw-Hill Charles A. Schuler.
1 Fundamentals of Microelectronics  CH1 Why Microelectronics?  CH2 Basic Physics of Semiconductors  CH3 Diode Circuits  CH4 Physics of Bipolar Transistors.
Inverting and non-inverting amplifier
William. Operational Amplifier (op amp) Drawing Circuit Diagrams Inverting Amplifiers – Negative potential is higher than Positive Potential Non-Inverting.
1 The Operational Amplifier continued The voltage follower provides unity gain, however, the output impedance is changed according to the o/p impedance.
UNIT – III : OP-AMPS AND APPLICATIONS
Fundamentals of Electric Circuits Chapter 5 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Op Amp Nonidealities (1) Section 8.4. Topics DC Offset Input Bias Current Speed Limitations Slew Rate Finite Input and Output Impedance.
1 Module 12 Operational Amplifiers – Part II 2 Review from Operational Amplifiers I: Negative inputPositive inputOutput V POS –V NEG Power Supply Voltages.
1 COMPARATORS Function: Compares two input voltages and produces an output in either of two states indicating the greater than or less than relationship.
OP-AMPs Op Amp is short for operational amplifier. An operational amplifier is modeled as a voltage controlled voltage source. An operational amplifier.
Operational Amplifiers
1 Chapter 8 Operational Amplifier as A Black Box  8.1 General Considerations  8.2 Op-Amp-Based Circuits  8.3 Nonlinear Functions  8.4 Op-Amp Nonidealities.
PRESENTATION ON:  Voltage Amplifier Presentation made by: GOSAI VIVEK ( )
مكبر العمليات Operational Amplifier Operational Amplifier and its circuit. Types of op-amp. Application of op- amp. Examples Operational Amplifier.
EE101-Lecture 8 Operational Amplifier Basics of amplifiers EE101 Fall 2012 Lect 8- Kang1 Noninverting amplifier & Inverting amplifier.
1 Operational Amplifiers 1. 2 Outlines Ideal & Non-ideal OP Amplifier Inverting Configuration Non-inverting Configuration Difference Amplifiers Effect.
Schmitt Trigger Circuits. Op Amps Previously in ET1 we investigated the Operational Amplifier. The Op Amp consisted of V in V out A feedback loop O V.
4-5-2 Regeneration. Regeneration In the previous topic we introduced the issues of attenuation, noise and distortion, and how they might affect a signal.
NON LINEAR IC APPLICATION USING OP AMP NAME:- ROLL NO. ROHAN V. KHRISTI 14ELEE310 AFJAL A. RATHOD 14ELEE311 NIKUNJ K. PARMAR 14ELEE312 SUB :- ANALOG ELECTRONIC.
EKT 314/4 WEEK 5 : CHAPTER 3 SIGNAL CONDITIONING ELECTRONIC INSTRUMENTATION.
An operational amplifier (Op-Amp) is a differential amplifier that amplifies the difference of voltages applied to its two input terminals (differential.
Module 2 Operational Amplifier Basics
Op-amp Comparators part I of 3
Electronics SL – Option C.3 HL – Option F.5. Operational Amplifier An amplifier is a device that takes a signal and makes its bigger. – An mp3 player.
More Non-Ideal Properties
OP-AMPS: basics & Inverting-amplifier
The Ideal Op Amp Inverting and non-Inverting configurations
The Ideal Op Amp Inverting and non-Inverting configurations
ELEC207 Linear Integrated Circuits
Presentation transcript:

More Non-Ideal Properties Bias Current Offset Voltage Saturation Applications of saturation

Bias Current All op-amps draw a small constant d.c. bias currents at their inputs. Typical value for a 741 is around 100 nA. This is only notable when very high impedance sources are used. In such cases, an alternative op-amp with lower bias current should be used. NB. Bias current is separate to input impedance. It is equivalent to a current source in parallel with the input impedance.

Offset Voltage When both input voltages are equal, the output should be zero. Actually it probably won’t be due to an offset voltage between the inputs. Typically, this is around 2 mV. This isn’t much but is magnified so much by the op- amp gain that it will probably saturate. Offset voltage is automatically compensated by a negative feedback network. Can be a problem for precision comparator applications.

D.C. Equivalent Circuit Both the offset voltage and bias current are d.c. A.C. operation is not affected by them (they just add an offset) Negative feedback reduces the effect of both Steps can be taken to reduce them (further reading)

Saturation V OUT cannot exceed the supply voltages. In fact, typically V OUT can only get to within about 1.5 V of the supplies.

Consequences of Saturation Unwanted when: Linear amplification was required Wanted when: A clipping effect is required (e.g. distortion effects popular with guitarists) Essential when: The op-amp is used as a comparator

Non-Linear Op-Amp Applications Applications using saturation Comparators Comparator with hysteresis (Schmitt trigger) Oscillators Applications using active feedback components Log, antilog, squaring etc. amplifiers Precision rectifier

Comparators If A 0 is large, practical response can be approximated as : V IN > 0  V + > V -  V OUT = +V SAT V IN < 0  V + < V -  V OUT = -V SAT

Microcap Demo 1

Hysteresis A comparator with hysteresis has a ‘safety margin’. One of two thresholds is used depending on the current output state. V time Upper threshold Lower threshold

Schmitt Trigger The Schmitt trigger is an op-amp comparator circuit featuring hysteresis. The inverting variety is the most commonly used.

Schmitt Trigger Analysis But, Switching occurs when:

Microcap Demo 2

Input-Output Relationship V IN V OUT +V THRESH 0 (i) +V SAT -V V IN increasing V IN V OUT -V THRESH 0 (ii) +V SAT -V V IN decreasing V IN V OUT +V THRESH 0 (iii) +V SAT -V -V THRESH (i) & (ii) combined

Asymmetrical Thresholds We don’t always want the threshold levels to be symmetrical around 0 V. More general configuration features an arbitrary reference level.

Analysis Using Kirchoff’s current law:

Realising V REF Solving often gives a value of V REF that isn’t available. Providingand But,

Summary Saturation of op-amps is exploited by comparator circuits. Their function is to decide whether an input voltage is greater or less than a reference level. Hysteresis is often applied to provide some resilience against noise.