DOCSLIB.ORG

A Fully Differential Cmos Operational Amplifier Implemented with Mos Gain Boosting Technique

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Fully Differential Cmos Operational Amplifier Implemented with Mos Gain Boosting Technique A FULLY DIFFERENTIAL CMOS OPERATIONAL AMPLIFIER IMPLEMENTED WITH MOS GAIN BOOSTING TECHNIQUE by PING LO, B.S.E.E. A THESIS IN ELECTRICAL ENGINEERING Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE IN ELECTRICAL ENGINEERING Approved Accepted May, 1996 I C^Cjk ACKNOWLEDGEMENTS I like to express my gratefulness to Professor Kwong Shu Chao, without whose thoughtful guidance and patience, the success of this work would never have been possible. I am also thankful to Professor Sunanda Mitra and Osamu Ishihara for their interest and advice in this work. I appreciate the support of my fellow students in the EE department, in particular, Ramesh M.C. for his circuit insight, and Stephen Bayne for his help in chip testing. Lastly, I would like to dedicate this thesis to my father, for his unprecedented love and support throughout my graduate studies. Without him, my study here would not have been possible. TABLE OF CONTENTS ACKNOWLEDGMENTS ii LISTOFTABLES v LIST OF FIGURES vi CHAPTER I. INTRODUCTION 1 1.1 Motivation 1 1.2 Structure of Thesis 3 II. OPERATIONAL AMPLIFIER DESIGN REVIEW 4 2.1 Performance Metrics 4 2.2 Differential Amplifiers 6 2.3 Operational Amplifier Toplogies 8 2.3.1 Multi-Stage Amplifier 8 2.3.2 Single Stage Amplifier 11 2.3.3 Gain Boosting Techniques 14 III. SUPER-MOST STRUCTURE 16 3.1 Overview of Current Mirror Structures 16 3.2 Principle of Super-MOST 19 3.3 Super-MOST Topologies 23 3.3.1 Topology 1 23 3.3.2 Topology 2 26 iii 3.4 Proposed New Structure 28 3.4.1 Circuit Analysis 30 3.4.2 Simulation Results 31 IV. DESIGN OF FULLY DIFFERENTIAL OPERATIONAL AMPLIFIER 38 4.1 Design considerations 39 4.2 Operational Amplifier Architecture 40 4.2.1 Comparisons of Single Stage and Two Stages Implementation 40 4.2.2 Comparisons of Single Ended and Differential Implementation 41 4.3 Circuit Description 42 4.3.1 Main Stage 42 4.3.2 Bias Circuit 48 4.3.3 Common Mode Feedback Circuit 49 4.4 Simulation Results 52 V. EXPERIMENTAL RESULTS 60 5.1 Description of Experimental Chip 60 5.2 Test Setup 61 5.3 Test Results 62 VI. CONCLUSION 69 REFERENCES 71 APPENDIX: MOSIS PROCESS PARAMETER 74 IV LIST OF TABLES 3.1 Dimensions of transistors in Super-MOST 33 4.1 Dimensions of transistors in the operational amplifier 58 4.2 Summary of fully differential operational amplifier performance 59 LIST OF FIGURES 2.1 Differential amplifier 6 2.2 AC equivalent model of the differential amplifier 8 2.3 Two-stage operational amplifier configuration 9 2.4 Telescopic cascode amplifier 12 2.5 Folded cascode operational amplifier 13 2.6 Mirrored cascode operational amplifier 13 2.7 Cascode Circuits 14 3.1 Cascode (a) transistors circuit, (b) small-signal equivalent circuit 17 3.2 Regulated cascode transistors 19 3.3 Simple Super-MOST structure 21 3.4 Modified Super-MOST structure 23 3.5 Super-MOST configuration 1 24 3.6 Super-MOST configuration 2 27 3.7 Proposed Super-MOST configuration 28 3.8 Symbols for (a) N-type, (b) P-type Super-MOST 29 3.9 Current-voltage characteristics of (a) a single n-transistor, (b) the N-type Super-MOST with KG-T ranging from-1.5 V to-1 V 34 3.10 Current-voltage characteristics of (a) a single p-transistor, (b) the P-type Super-MOST with KGS ranging from 1 V to 1.5 V 35 3.11 Simulation result of the current mirror using N-type Super-MOST with /,„ ranging from 40 (xA to 200 fxA 36 VI 3.12 Frequency response of the inverting amplifier 37 3.13 Output voltage swing of the inverting amplifier 37 4.1 Main stage of the fully differential operational amplifier 43 4.2 Equivalent circuit of the Super-MOST 44 4.3 Equivalent circuit for the input differential pair 45 4.4 Small signal equivalent half circuit of the main stage 47 4.5 Bias circuit 48 4.6 Simplified configuration of a fully differential switched capacitor network . 50 4.7 Common mode feedback circuit 51 4.8 Frequency reponse of the fully differential operational amplifier (a) magnitude plot, (b) phase plot 53 4.9 Step response of the fully differential operational amplifier with (a)±0.2V,(b)± 1.5 V input 54 4.10 Output voltage swing of the fully differential amplifier 55 4.11 Transient response with 5 mV sinusoidal input 56 4.12 Output response of an integrator implemented with the operational amplifier 57 4.13 Output response of a differentiator implemented with the operational amplifier 57 5.1 Layout of the experimental chip 64 5.2 Die photo of the experimental chip 65 5.3 Measured current-voltage characteristics of N-type Super-MOST 66 5.4 Measured current-voltage characteristics of P-type Super-MOST 66 vu 5.5 Input and output waveforms of the operational amplifier for (a) frequency of 2 kHz, and (b) frequency of 200 kHz 67 5.6 Input and output waveforms for frequency varied sinusoidal signal in the range of (a) hundred-ldlo-Hz, and (b) mega-Hz 68 vm CHAPTER I INTRODUCTION 1.1 Motivation CMOS technologies have rapidly improved over the past few years. To date, the size of transistor is shrunk to sub-micron and fabrication processes attain finesse, resulting in dramatic increases in the speed and density of integrated circuit devices. The result of this trend is the system on a chip, in which aU circuitry wiU be housed within a couple of square centimeter of die area, in particular for a large digital system. Compared with their analog counterparts, digital circuits are less susceptible to noise and more endurance to the supply and process variations, and allow easier design and test automation. These facts contribute to more digital circuits and less analog circuits being integrated within a chip. However, since naturally occurring signals are analog, in order to perform any digital signal processing (DSP), data conversion system is needed to digitize the signal at the input and reproduce the signal at the output. For example, applications such as high definition television (HDTV), compact disc players, CD ROM, and modems, as well as special systems such as medical imaging, speech processing, and radar employ data conversion systems for interfacing. As the demand for these high performance appUcations increases, the design of data conversion system becomes increasingly difficult. This is because a high speed and high accuracy analog circuit is not easy to attain, and tradeoff often has to be made. Furthermore, in the mixed signal system, analog portions 1 are susceptible to the coupling noise via power supply, substrate current and crosstalk of adjacent line during digital switching. As a result, mixed signal system designs become a challenging problem. In most of the data conversion systems, such as switched capacitor circuits [1], sigma-delta converters [2], pipeline A/D converters [3], [4], algorithmic A/D converters [5], [6], and sample-and-hold amplifiers [7], [8], operational ampUfiers form the basic building block. High gain and high unity gain frequency amplifiers are needed to meet the requirements for high performance systems. Satisfying both of these requirements, however, is difficult to achieve since high unity gain frequency calls for short channel devices which has low intrinsic gain. Therefore, gain enhancement techniques are necessary for designing a high gain and high unity gain frequency operational amplifier. This thesis investigates the gain boosting technique proposed by K.Bult and G. Geelen [9]. An improved cascode circuit that combines both high gain and high speed is developed. Using this cascode circuit, a high performance fully differential operational amplifier is designed. A prototype of the cascode circuit and operational ampUfier was fabricated in a 2 |im n-well CMOS technology. Simulation results indicate that the cascode circuit has at least 100 MQ output impedance, while the amplifier has an open loop gain of 98 dB and a unity gain frequency of 17 MHz for 10 pF load capacitor. 1.2 Structure of Thesis This thesis is outlined as follows. Chapter n analyzes a differential amplifier, which is the building block for an operational amplifier. Various operational amplifier topologies are also examined with emphasis on the speed and gain analysis. Some previous works are studied and their performance limitations are discussed. In chapter in, the problems associated with the conventional cascode circuits are identified and an improved version of cascode circuit, which is called Super-MOST, is introduced. Also presented is the principle and operation of the Super-MOST. Two previous designs using this principle are then described along with their drawbacks. A new topology is proposed that has superior performance over the two previous design. Chapter IV describes the design of the fuUy differential operational amplifier. The reasons of choosing the topology are explained. Also, a common mode feedback stage is presented that is employed to control the output bias point. Chapter V shows the experimental results from a prototype chip which includes the Super-MOST and the operational amplifier. In chapter VI, the summary of this research and the suggestions for future work are presented. CHAPTER II OPERATIONAL AMPLIHER DESIGN REVIEW This chapter presents an overview of some of previous CMOS operational amplifier configurations, but stand alone designs are not addressed. Since this research is focused on designing an operational amplifier that can be used as a building block for analog signal processing system, the primary emphasis in this chapter is placed on the factors affecting the gain and speed of an operational amplifier.
Load more

Recommended publications
  • 1.5A, 24V, 17Mhz Power Operational Amplifier Datasheet (Rev. E)
    OPA564 www.ti.com SBOS372E –OCTOBER 2008–REVISED JANUARY 2011 1.5A, 24V, 17MHz POWER OPERATIONAL AMPLIFIER Check for Samples: OPA564 1FEATURES 23• HIGH OUTPUT CURRENT: 1.5A DESCRIPTION • WIDE POWER-SUPPLY RANGE: The OPA564 is a low-cost, high-current operational – Single Supply: +7V to +24V amplifier that is ideal for driving up to 1.5A into reactive loads. The high slew rate provides 1.3MHz – Dual Supply: ±3.5V to ±12V full-power bandwidth and excellent linearity. These • LARGE OUTPUT SWING: 20VPP at 1.5A monolithic integrated circuits provide high reliability in • FULLY PROTECTED: demanding powerline communications and motor control applications. – THERMAL SHUTDOWN – ADJUSTABLE CURRENT LIMIT The OPA564 operates from a single supply of 7V to 24V, or dual power supplies of ±3.5V to ±12V. In • DIAGNOSTIC FLAGS: single-supply operation, the input common-mode – OVER-CURRENT range extends to the negative supply. At maximum – THERMAL SHUTDOWN output current, a wide output swing provides a 20VPP (I = 1.5A) capability with a nominal 24V supply. • OUTPUT ENABLE/SHUTDOWN CONTROL OUT • HIGH SPEED: The OPA564 is internally protected against over-temperature conditions and current overloads. It – GAIN-BANDWIDTH PRODUCT: 17MHz is designed to provide an accurate, user-selected – FULL-POWER BANDWIDTH AT 10VPP: current limit. Two flag outputs are provided; one 1.3MHz indicates current limit and the second shows a – SLEW RATE: 40V/ms thermal over-temperature condition. It also has an Enable/Shutdown pin that can be forced low to shut • DIODE FOR JUNCTION TEMPERATURE down the output, effectively disconnecting the load. MONITORING The OPA564 is housed in a thermally-enhanced, • HSOP-20 PowerPAD™ PACKAGE surface-mount PowerPAD™ package (HSOP-20) with (Bottom- and Top-Side Thermal Pad Versions) the choice of the thermal pad on either the top side or the bottom side of the package.
    [Show full text]
  • Designing Linear Amplifiers Using the IL300 Optocoupler Application Note
    Application Note 50 Vishay Semiconductors Designing Linear Amplifiers Using the IL300 Optocoupler INTRODUCTION linearizes the LED’s output flux and eliminates the LED’s This application note presents isolation amplifier circuit time and temperature. The galvanic isolation between the designs useful in industrial, instrumentation, medical, and input and the output is provided by a second PIN photodiode communication systems. It covers the IL300’s coupling (pins 5, 6) located on the output side of the coupler. The specifications, and circuit topologies for photovoltaic and output current, IP2, from this photodiode accurately tracks the photoconductive amplifier design. Specific designs include photocurrent generated by the servo photodiode. unipolar and bipolar responding amplifiers. Both single Figure 1 shows the package footprint and electrical ended and differential amplifier configurations are discussed. schematic of the IL300. The following sections discuss the Also included is a brief tutorial on the operation of key operating characteristics of the IL300. The IL300 photodetectors and their characteristics. performance characteristics are specified with the Galvanic isolation is desirable and often essential in many photodiodes operating in the photoconductive mode. measurement systems. Applications requiring galvanic isolation include industrial sensors, medical transducers, and IL300 mains powered switchmode power supplies. Operator safety 1 8 and signal quality are insured with isolated interconnections. These isolated interconnections commonly use isolation 2 K2 7 amplifiers. K1 Industrial sensors include thermocouples, strain gauges, and pressure transducers. They provide monitoring signals to a 3 6 process control system. Their low level DC and AC signal must be accurately measured in the presence of high 4 5 common-mode noise.
    [Show full text]
  • NTE7144 Integrated Circuit BIMOS Operational Amplifier W/MOSFET Input, Bipolar Output
    NTE7144 Integrated Circuit BIMOS Operational Amplifier w/MOSFET Input, Bipolar Output Description: The NTE7144 is an integrated circuit operational amplifier in an 8–Lead Mini–DIP type package that combines the advantages of high–voltage PMOS transistors with high–voltage bipolar transistors on a single monolithic chip. This device features gate–protected MOSFET (PMOS) transistors in the in- put circuit to provide very–high–input impedance, very–low–input current, and high–speed perfor- mance. The NTE7144 operates at supply voltages from 4V to 36V (either single or dual supply) and is internally phase–compensated to achieve stable operation in unity–gain follower operation. The use of PMOS field–effect transistors in the input stage results in common–mode input–voltage capability down to 0.5V below the negative–supply terminal, an important attribute for single–supply applications. The output stage uses bipolar transistors and includes built–in protection against dam- age from load–terminal short–circuiting to either supply–rail or to GND. Features: D MOSFET Input Stage: Very High Input Impedance Very Low Input Current Wide Common–Mode Input Voltage Range Output Swing Complements Input Common–Mode Range D Directly Replaces Industry Type 741 in Most Applications Applications: D Ground–Referenced Single–Supply Amplifiers in Automobile and Portable Instrumentation D Sample and Hold Amplifiers D Long–Duration Timers/Multivibrators (Microseconds – Minutes – Hours) D Photocurrent Instrumentation D Peak Detectors D Active Filters D Comparators D Interface in 5V TTL Systems and other Low–Supply Voltage Systems D All Standard Operational Amplifier Applications D Function Generators D Tone Controls D Power Supplies D Portable Instruments D Intrusion Alarm Systems Absolute Maximum Ratings: DC Supply Voltage (Between V+ and V– Terminals).
    [Show full text]
  • Chapter 10 Differential Amplifiers
    Chapter 10 Differential Amplifiers 10.1 General Considerations 10.2 Bipolar Differential Pair 10.3 MOS Differential Pair 10.4 Cascode Differential Amplifiers 10.5 Common-Mode Rejection 10.6 Differential Pair with Active Load 1 Audio Amplifier Example An audio amplifier is constructed as above that takes a rectified AC voltage as its supply and amplifies an audio signal from a microphone. CH 10 Differential Amplifiers 2 “Humming” Noise in Audio Amplifier Example However, VCC contains a ripple from rectification that leaks to the output and is perceived as a “humming” noise by the user. CH 10 Differential Amplifiers 3 Supply Ripple Rejection vX Avvin vr vY vr vX vY Avvin Since both node X and Y contain the same ripple, their difference will be free of ripple. CH 10 Differential Amplifiers 4 Ripple-Free Differential Output Since the signal is taken as a difference between two nodes, an amplifier that senses differential signals is needed. CH 10 Differential Amplifiers 5 Common Inputs to Differential Amplifier vX Avvin vr vY Avvin vr vX vY 0 Signals cannot be applied in phase to the inputs of a differential amplifier, since the outputs will also be in phase, producing zero differential output. CH 10 Differential Amplifiers 6 Differential Inputs to Differential Amplifier vX Avvin vr vY Avvin vr vX vY 2Avvin When the inputs are applied differentially, the outputs are 180° out of phase; enhancing each other when sensed differentially. CH 10 Differential Amplifiers 7 Differential Signals A pair of differential signals can be generated, among other ways, by a transformer.
    [Show full text]
  • Example of a MOSFET Operational Amplifier
    Example of a MOSFET Operational Amplifier: This circuit is one I “designed” as an example for Engineering 1620. It is certainly not fully optimized and I am not sure it is free of errors. It is based on a 1.5 micron, P-well process and therefore uses an N-channel differential pair for its input. This is somewhat unusual because P-channel devices have lower intrinsic noise and are the device-type of choice for the input stage. I did this simply to avoid doing your SPICE assignment for you. The overall properties of the circuit are given in the table below. Amplifier Property Value A0 – DC Gain 86 DB (X20,000) fp – dominant pole position 400 Hz fGBW 8.0 MHz fU – unity gain frequency 5.6 MHz Output stage resistance at low frequency 277 K Zero position 10.7 MHz Slew Rate 710 6 V/sec Output stage quiescent current 65 a Opamp quiescent current 103 a Bias circuit quiescent current 104 a Total system quiescent current 210 a VDD 5.0 volts Total system power 1.1 mW MOSFET Operational Amplifier Gain and Phase 10 0 18 0 80 12 0 60 Gain 60 Phase 40 0 Gain (DB) 20 -60 Phase (deg.) 0 -120 -20 -180 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08 Frequency (Hz) Phase margin = 60 deg. Parameter Table for MOSFET Opamp Example element model vds vgs vth vov id gm ro m1 nssb 0.748 0.851 0.547 0.304 3.77E-05 2.90E-04 5.54E+05 m10 nssb 3.368 0.851 0.547 0.304 4.12E-05 3.11E-04 8.09E+05 m12 nssb 0.711 0.711 0.546 0.165 3.51E-05 5.01E-04 5.05E+05 m13 nssb 0.838 0.851 0.547 0.304 3.79E-05 2.91E-04 5.92E+05 m14 nssb 3.078 1.079 0.840 0.239 3.51E-05
    [Show full text]
  • AN55 Power Supply Bypassing for High-Voltage Operational Amplifiers
    AN55 Power Supply Bypassing for High-Voltage Operatinal Amplifiers POWER SUPPLY BYPASSING FOR HIGH-VOLTAGE OPERATIONAL AMPLIFIERS With the introduction of Apex’s high-voltage amplifiers like PA89 and PA99, new issues arise in the realm of circuit board layout and power supply bypassing. Working with these amplifiers, designers quickly realize that the same rules do not apply between bypassing high- and low-voltage Op-Amps. This applications infor- mation is meant to assist in designing the bypass system in a high-voltage operational amplifier circuit and choosing the perfect capacitors for use in such designs. THE NEED FOR POWER SUPPLY BYPASSING Before finding a couple of high-voltage capacitors and tacking them onto your supply rails, it is vital to realize the purpose of these capacitors and what we need them to do. Power supply bypass capacitors are there to stabilize the supply voltages of a circuit. Logically, the next question to answer would be, “What causes supply voltages to change?” This list can go on, but the most common reasons for changing supply voltages are power interruptions, high-frequency voltage/current spikes, and high-current draws. Figure 1: Power Supply Rejection Chart of PA89 100 80 60 40 20 WŽǁĞƌ^ƵƉƉůLJZĞũĞĐƟŽŶ͕W^Z;ĚͿ 0 1 10100 1k 10k 100k1M 10M Frequency, F (Hz) The first two entries on the list can be lumped into one category called “high-frequency events.” One close look at the datasheet for PA89 yields the Power Supply Rejection chart. As the frequency increases, power supply rejection falls off rather quickly. For example, if the power supply rail experiences a 100 kHz spike, then as much as 1% of that high-frequency voltage change will show up on the output.
    [Show full text]
  • Differential Amplifiers
    www.getmyuni.com Operational Amplifiers: The operational amplifier is a direct-coupled high gain amplifier usable from 0 to over 1MH Z to which feedback is added to control its overall response characteristic i.e. gain and bandwidth. The op-amp exhibits the gain down to zero frequency. Such direct coupled (dc) amplifiers do not use blocking (coupling and by pass) capacitors since these would reduce the amplification to zero at zero frequency. Large by pass capacitors may be used but it is not possible to fabricate large capacitors on a IC chip. The capacitors fabricated are usually less than 20 pf. Transistor, diodes and resistors are also fabricated on the same chip. Differential Amplifiers: Differential amplifier is a basic building block of an op-amp. The function of a differential amplifier is to amplify the difference between two input signals. How the differential amplifier is developed? Let us consider two emitter-biased circuits as shown in fig. 1. Fig. 1 The two transistors Q1 and Q2 have identical characteristics. The resistances of the circuits are equal, i.e. RE1 = R E2, RC1 = R C2 and the magnitude of +VCC is equal to the magnitude of �VEE. These voltages are measured with respect to ground. To make a differential amplifier, the two circuits are connected as shown in fig. 1. The two +VCC and �VEE supply terminals are made common because they are same. The two emitters are also connected and the parallel combination of RE1 and RE2 is replaced by a resistance RE. The two input signals v1 & v2 are applied at the base of Q1 and at the base of Q2.
    [Show full text]
  • A Differential Operational Amplifier Circuit Collection
    Application Report SLOA064A – April 2003 A Differential Op-Amp Circuit Collection Bruce Carter High Performance Linear Products ABSTRACT All op-amps are differential input devices. Designers are accustomed to working with these inputs and connecting each to the proper potential. What happens when there are two outputs? How does a designer connect the second output? How are gain stages and filters developed? This application note answers these questions and gives a jumpstart to apprehensive designers. 1 INTRODUCTION The idea of fully-differential op-amps is not new. The first commercial op-amp, the K2-W, utilized two dual section tubes (4 active circuit elements) to implement an op-amp with differential inputs and outputs. It required a ±300 Vdc power supply, dissipating 4.5 W of power, had a corner frequency of 1 Hz, and a gain bandwidth product of 1 MHz(1). In an era of discrete tube or transistor op-amp modules, any potential advantage to be gained from fully-differential circuitry was masked by primitive op-amp module performance. Fully- differential output op-amps were abandoned in favor of single ended op-amps. Fully-differential op-amps were all but forgotten, even when IC technology was developed. The main reason appears to be the simplicity of using single ended op-amps. The number of passive components required to support a fully-differential circuit is approximately double that of a single-ended circuit. The thinking may have been “Why double the number of passive components when there is nothing to be gained?” Almost 50 years later, IC processing has matured to the point that fully-differential op-amps are possible that offer significant advantage over their single-ended cousins.
    [Show full text]
  • 9 Op-Amps and Transistors
    Notes for course EE1.1 Circuit Analysis 2004-05 TOPIC 9 – OPERATIONAL AMPLIFIER AND TRANSISTOR CIRCUITS . Op-amp basic concepts and sub-circuits . Practical aspects of op-amps; feedback and stability . Nodal analysis of op-amp circuits . Transistor models . Frequency response of op-amp and transistor circuits 1 THE OPERATIONAL AMPLIFIER: BASIC CONCEPTS AND SUB-CIRCUITS 1.1 General The operational amplifier is a universal active element It is cheap and small and easier to use than transistors It usually takes the form of an integrated circuit containing about 50 – 100 transistors; the circuit is designed to approximate an ideal controlled source; for many situations, its characteristics can be considered as ideal It is common practice to shorten the term "operational amplifier" to op-amp The term operational arose because, before the era of digital computers, such amplifiers were used in analog computers to perform the operations of scalar multiplication, sign inversion, summation, integration and differentiation for the solution of differential equations Nowadays, they are considered to be general active elements for analogue circuit design and have many different applications 1.2 Op-amp Definition We may define the op-amp to be a grounded VCVS with a voltage gain (µ) that is infinite The circuit symbol for the op-amp is as follows: An equivalent circuit, in the form of a VCVS is as follows: The three terminal voltages v+, v–, and vo are all node voltages relative to ground When we analyze a circuit containing op-amps, we cannot use the
    [Show full text]
  • 621 212 Electronics and Communication Engineering Ec6304/Linear Integrated Circuits
    DSEC/ECE/EC6304-LIC/QB 1 DHANALAKSHMI SRINIVASAN ENGINEERING COLLEGE -621 212 ELECTRONICS AND COMMUNICATION ENGINEERING EC6304/LINEAR INTEGRATED CIRCUITS QUESTION BANK UNIT 1(2 MARKS) 1. What is an integrated circuit? APRIL/MAY 2010 An integrated circuit (IC) is a miniature, low cost electronic circuit consisting of active and Passive components fabricated together on a single crystal of silicon. The active components are Transistors and diodes and passive components are resistors and capacitors. 2. What is current mirror? APRIL/MAY 2010 A constant current source (current mirror) makes use of the fact that for a transistor in the active mode of operation, the collector current is relatively independent of the collector voltage 3. What are two requirements to be met for a good current source? MAY/JUNE 2012 a. Superior insensitivity of circuit performance to power supply variations and temperature. b. More economical than resistors in terms of die area required providing bias currents of small value. c. When used as load element, the high incremental resistance of current source results in high voltage gains at low supply voltages. 4. What are all the important characteristics of ideal op-amp? APRIL/MAY 2015 Ideal characteristics of OPAMP 1. Open loop gain infinite 2. Input impedance infinite 3. Output impedance low 4. Bandwidth infinite 5. Zero offset, ie, Vo=0 when V1=V2=0 5. Define CMRR of OP-AMP APRIL/MAY 2011 The relative sensitivity of an op-amp to a difference signal as compared to a common - mode signal is called the common -mode rejection ratio. It is expressed in decibels.
    [Show full text]
  • Fully-Differential Amplifiers
    Application Report S Fully-Differential Amplifiers James Karki AAP Precision Analog ABSTRACT Differential signaling has been commonly used in audio, data transmission, and telephone systems for many years because of its inherent resistance to external noise sources. Today, differential signaling is becoming popular in high-speed data acquisition, where the ADC’s inputs are differential and a differential amplifier is needed to properly drive them. Two other advantages of differential signaling are reduced even-order harmonics and increased dynamic range. This report focuses on integrated, fully-differential amplifiers, their inherent advantages, and their proper use. It is presented in three parts: 1) Fully-differential amplifier architecture and the similarities and differences from standard operational amplifiers, their voltage definitions, and basic signal conditioning circuits; 2) Circuit analysis (including noise analysis), provides a deeper understanding of circuit operation, enabling the designer to go beyond the basics; 3) Various application circuits for interfacing to differential ADC inputs, antialias filtering, and driving transmission lines. Contents 1 Introduction . 3 2 What Is an Integrated, Fully-Differential Amplifier? . 3 3 Voltage Definitions . 5 4 Increased Noise Immunity . 5 5 Increased Output Voltage Swing . 6 6 Reduced Even-Order Harmonic Distortion . 6 7 Basic Circuits . 6 8 Circuit Analysis and Block Diagram . 8 9 Noise Analysis . 13 10 Application Circuits . 15 11 Terminating the Input Source . 15 12 Active Antialias Filtering . 20 13 VOCM and ADC Reference and Input Common-Mode Voltages . 23 14 Power Supply Bypass . 25 15 Layout Considerations . 25 16 Using Positive Feedback to Provide Active Termination . 25 17 Conclusion . 27 1 SLOA054E List of Figures 1 Integrated Fully-Differential Amplifier vs Standard Operational Amplifier.
    [Show full text]
  • E Basic Circuit of an Operational Amplifier Is As Shown in Above Fig
    www.getmyuni.com UNIT - 1 OPERATIONAL AMPLIFIER FUNDAMENTALS 1.1 Basic operational amplifier circuit- heT basic circuit of an operational amplifier is as shown in above fig. has a differential amplifier input stage and an emitter follower output. Supply voltages +Vcc and -Vcc are provided. Transistors Q1 and Q2 constitute a differential amplifier, which produces a voltage change as the collector of Q2 where a difference input voltage is applied to the bases of Q1 and Q2. Transistor Q2 operates as an emitter follower to provide low output impedance. Vo = Vcc –VRC –VBE3 = Vcc – IC2Rc – VBE Assume that Q1 and Q2 are matched transistors that are they have equal VBE levels and equalcurrent gains. With both transistor bases at ground level, the emitter currents are equal and both IE1 and IE2 flow through the common emitter resistor RE. The emitter current is given by:- www.getmyuni.com IE1 + IE2 = VRE/RE With Q1 and Q2 bases grounded, 0 – VBE – VRE + VEE = 0 VEE – VBE = VRE VRE = VEE – VBE IE1 + IE2 = – Vcc = 10 V, VEE = - 10 V, RE = 4.7 K, Rc = 6.8 K, VBE = 0.7, IE1 + IE2 = (10 – 0.7)/4.7 K + 2 mA IE1 = IE2 = 1mA Ic2 = IE2 = 1 mA Vo = 10 – 1mA x 6.8 K – 0.7 Vo = 2.5 V If a positive going voltage is applied to the non-inverting input terminal, Q1 base is pulled up by the input voltage and its emitter terminal tends to follow the input signal. Since Q1 and Q2 emitters are connected together, the emitter of Q2 is also pulled up by the positive going signal at the non-inverting input terminal.
    [Show full text]