DOCSLIB.ORG

Philadelphia University Amplifier Circuits-III

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Philadelphia University Amplifier Circuits-III Module: Electronics II Module Number: 650321 Electronic Devices and Circuit Theory, 9th ed., Boylestad and Nashelsky Philadelphia University Faculty of Engineering Communication and Electronics Engineering Amplifier Circuits-III Operational Amplifiers (Op-Amps): An operational amplifier, or op-amp, is a very high gain differential amplifier with high input impedance and low output impedance. Typical uses of the operational amplifier are to provide voltage amplitude changes (amplitude and polarity), oscillators, filter circuits, and many types of instrumentation circuits. An op-amp contains a number of differential amplifier stages to achieve a very high voltage gain. - Symbol and Terminals: The following Figure shows a basic op-amp with two inputs and one output as would result using a differential amplifier input stage. Each input results in either the same or an opposite polarity (or phase) output, depending on whether the signal is applied to the plus (+) or the minus (-) input. To illustrate what an op-amp is, let's consider its ideal characteristics. A practical op- amp, of course, falls short of these ideal standards, but it is much easier to understand and analyze the device from an ideal point of view. These two considerations are clearly shown in the Figure Below. Firstly, the ideal op-amp has - infinite voltage gain, - infinite bandwidth, - it has an infinite input impedance (open) so that it does not load the driving source, - a zero output impedance. Lecturer: Dr. Omar Daoud Part III 1 Module: Electronics II Module Number: 650321 Electronic Devices and Circuit Theory, 9th ed., Boylestad and Nashelsky The input voltage, Vin appears between the two input terminals, and the output voltage is AvVin as indicated by the internal voltage source symbol. Secondly, characteristics of a practical op-amp are: - very high voltage gain, - very high input impedance, - low output impedance, and - wide bandwidth. - Internal Block Diagram: A typical op-amp is made up of three types of amplifier circuit: a differential amplifier, a voltage amplifier, and a push-pull amplifier, as shown in the Figure below. A differential amplifier is the input stage for the op-amp; it provides amplification of the difference voltage between the two inputs. The second stage is usually a class A amplifier that provides additional gain. Some op-amps may have more than one voltage amplifier stage. A push-pull class B amplifier is typically used for the output stage. Lecturer: Dr. Omar Daoud Part III 2 Module: Electronics II Module Number: 650321 Electronic Devices and Circuit Theory, 9th ed., Boylestad and Nashelsky The Differential Amplifier Input Stage The term differential comes from the amplifier's ability to amplify the difference of two input signals applied to its inputs . Only the difference in the two signals is amplified; if there is no difference, the output is zero . A basic differential amplifier circuit and its symbol are shown in the Figure. The transistors (Q1 and Q2) and the collector resistors (Rc1 and Rc2) are carefully matched to have identical characteristics. Notice that the two transistors share a single emitter resistor, RE. The Differential Amplifier Operation: - Assume both bases are connected to ground, - The emitter voltage will be -0.7 V because the voltage drops across both base- emitter junctions are equa1. - The emitter currents are equal (IE1 = IE2) and each is one-half of the current through RE. - The collector currents are both equal and are approximately equal to the emitter currents. Because the collector currents are the same, the collector voltages are also the same, which reflects the zero difference in the input voltages (both bases are at 0V. - If the base of Q1 is disconnected from ground and connected to a small positive voltage, - Ql will conduct more current because the positive voltage on its base causes the emitter voltage to increase slightly. - Although the emitter voltage is a little higher, the total current through RE is nearly the same as before. - The emitter current is now divided so that more of it is in Ql and less in Q2. - As a result, the collector voltage of Q1 will decrease and the collector voltage of Q2 will increase, reflecting the difference in the input voltages (one is 0 V and the other at a small positive value). Lecturer: Dr. Omar Daoud Part III 3 Module: Electronics II Module Number: 650321 Electronic Devices and Circuit Theory, 9th ed., Boylestad and Nashelsky - If the base of Ql is placed back at ground and a small positive voltage is connected to the base of Q2, - Q2 will conduct more current, - Ql will conduct less, - The emitter current is now divided so that more of it is in Q2 and less in Q1, - As a result, the collector voltage of Q1 will increase and the collector voltage of Q2 will decrease. - The differential amplifier exhibits three modes of operation based on the type of input signals. These modes are single-ended, differential, and common. Since the differential amplifier is the input stage of the op-amp, the op-amp exhibits the same modes. Op-Amp Input Modes and Parameters 1) Input Signal Modes Single-Ended Mode: one input is grounded and a signal voltage is applied only to the other input. - In the case where the signal voltage is applied to the inverting input, an inverted, amplified signal voltage appears at the output. - In the case where the signal is applied to the noninverting input with the inverting input grounded, a non inverted, amplified signal voltage appears at the output. Differential Input Mode: Two opposite-polarity (out-of-phase) signals are applied to the inputs. This type of operation is also referred to as double- ended. The amplified difference between the two inputs appears on the output. Lecturer: Dr. Omar Daoud Part III 4 Module: Electronics II Module Number: 650321 Electronic Devices and Circuit Theory, 9th ed., Boylestad and Nashelsky Common Mode Input: Two signal voltages of the same phase, frequency, and amplitude are applied to the two inputs. When equal input signals are applied to both inputs, they cancel, resulting in a zero output voltage. This action is called common-mode rejection. Its importance lies in the situation where an unwanted signal appears commonly on both op-amp inputs. 2) Input Parameters Common Mode Rejection Ratio: Common-mode rejection means that this unwanted signal will not appear on the output and distort the desired signal. Common-mode signals (noise) generally are the result of the pick-up of radiated energy on the input lines, from adjacent lines, the 60 Hz power line, or other sources. The measure of an amplifier's ability to reject common-mode signals is a parameter called the CMRR (common-mode rejection ratio). where Ad = differential gain of the amplifier Ac = common-mode gain of the amplifier Vd = difference voltage Vc = common voltage Ex. Calculate the CMRR for the circuit measurements shown in Fig. Lecturer: Dr. Omar Daoud Part III 5 Module: Electronics II Module Number: 650321 Electronic Devices and Circuit Theory, 9th ed., Boylestad and Nashelsky Solution: Ex. Determine the output voltage of an op-amp for input voltages of Vi1 = 150 V, Vi2 =140 V. The amplifier has a differential gain of Ad = 4000 and the value of CMRR is: (a) 100. (b) 105. Solution: Lecturer: Dr. Omar Daoud Part III 6 Module: Electronics II Module Number: 650321 Electronic Devices and Circuit Theory, 9th ed., Boylestad and Nashelsky Common mode Input voltage range: It is the range of input voltages which, when applied to both inputs, will not cause clipping or other output distortion. Many op-amps have common-mode input voltage ranges of ±10 V with dc supply voltages of ±15 V. Input Impedance: Two basic ways of specifying the input impedance of an op-amp are the differential and the common mode. The differential input impedance is the total resistance between the inverting and the noninverting inputs (measured by determining the change in bias current for a given change in differential input voltage). The common-mode input impedance is the resistance between each input and ground (measured by determining the change in bias current for a given change in common-mode input voltage). Input Offset Voltage: The ideal op-amp produces zero volts out for zero volts in. In a practical op-amp, however, a small de voltage. VOUT(error), appears at the output when no differential input voltage is applied (causes a slight mismatch of the base-emitter voltages of the differential amplifier input stage of an op-amp) . The input offset voltage, Vos, is the differential dc voltage required between the inputs to force the output to zero volts (Typical values of in the range of 2 mV or less, while it is 0V in ideal cases). Input Offset Current: Ideally, the two input bias currents are equal, and thus their difference is zero. In a practical op-amp, however, the bias currents are not exactly equal. The input offset current, Ios, is the difference of the input bias currents, expressed as an absolute value (Actual magnitudes of offset current are usually at least an order of magnitude (ten times) less than the bias current). VIRIRIIRos 1 in 2 in 1 2 in VIRos os in VOUT (error) AIRv os in Lecturer: Dr. Omar Daoud Part III 7 Module: Electronics II Module Number: 650321 Electronic Devices and Circuit Theory, 9th ed., Boylestad and Nashelsky Slew Rate: The maximum rate of change of the output voltage in response to a step input voltage is the slew rate of an op-amp. The slew rate is dependent upon the high-frequency response of the amplifier stages within the op-amp. A pulse is applied to the input and the resulting ideal output voltage is indicated as below.
Load more

Recommended publications
  • 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]
  • 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]
  • 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]
  • Mosfet Differential Amplifier (Two-Week Lab)
    page 1 of 7 MOSFET DIFFERENTIAL AMPLIFIER (TWO-WEEK LAB) BACKGROUND The MOSFET is by far the most widely used transistor in both digital and analog circuits, and it is the backbone of modern electronics. One of the most common uses of the MOSFET in analog circuits is the construction of differential amplifiers. The latter are used as input stages in op-amps, video amplifiers, high-speed comparators, and many other analog-based circuits. MOSFET differential amplifiers are used in integrated circuits, such as operational amplifiers, they provide a high input impedance for the input terminals. A properly designed differential amplifier with its current-mirror biasing stages is made from matched-pair devices to minimize imbalances from one side of the differential amplifier to the other. In this lab, you will design a differential amplifier by first verifying its operation in PSPICE, then building and testing your circuit stage by stage. In your lab kit, you will find one or more CD4007 integrated circuits. (The letter prefix may vary; it's the number 4007 that matters.) This IC contains a number of NMOS and PMOS devices, as shown below. You may assume that all the NMOS transistors are matched to each other (same value of K and threshold voltage VTR), and that all the PMOS devices are similarly matched to each other. Use the devices in this integrated circuit when building your differential amplifier, as requested in Levels 2 and 3. page 2 of 7 BACKGROUND The general topology of a differential amplifier is shown below. Two active devices are connected to a positive voltage supply via passive series elements.
    [Show full text]
  • Lsk389 Application Note Dual Monolithic Jfet for Ultra-Low Noise Applications
    Over 30 Years of Quality Through Innovation LSK389 APPLICATION NOTE DUAL MONOLITHIC JFET FOR ULTRA-LOW NOISE APPLICATIONS By: Bob Cordell 01/21/2020 REV. A3 Linear Integrated Systems • 4042 Clipper Court • Fremont, CA 94538 • Tel: 510 490-9160 • Fax: 510 353-0261 • Email: [email protected] LINEAR SYSTEMS LSK389 DUAL MONOLITHIC JFET FOR ULTRA-LOW NOISE APPLICATIONS Features Applications ▪ Low Wideband Noise ▪ Low Noise Amplifiers ▪ Low 1/f Noise ▪ Differential Amplifiers ▪ High Transconductance ▪ High Input Impedance Amplifiers ▪ Well-Matched Threshold Voltages ▪ Phono and Other Audio Preamps ▪ High gm/Capacitance Ratio ▪ Condenser Microphone Preamps ▪ Industry's First 100% Noise-Tested JFET ▪ Electrometers ▪ Piezoelectric Sensor Preamps ▪ Front-end for Low-Noise Op Amps Introduction The LSK389 is the industry’s lowest noise Dual N-Channel JFET, 100% tested, guaranteed to meet 1/f and broadband noise specifications, while eliminating burst (RTN or popcorn) noise entirely. The product displays high transconductance and very good matching. It is the JFET of choice for low noise applications, especially those requiring a differential amplifier input stage. LSK389 Key Specifications ▪ 1.3 nV/√Hz input noise at 1 kHz, ID = 2 mA ▪ 1.5 nV/√Hz at 10 Hz, ID = 2 mA ▪ 14 mS transconductance at ID = 2 mA ▪ Improved DC offset ±15 mV max. ▪ CISS = 25 pF typ. ▪ CRSS = 5.5 pF typ. ▪ Breakdown voltage = 40 V min. ▪ 4 grades of IDSS available (A, B, C, D) N-Channel JFET Basics The simplified equation below describes the DC operation of a JFET [1]. The term Vt is the threshold voltage. The term is the transconductance coefficient of the JFET (not to be confused with BJT current gain).
    [Show full text]
  • Fully Differential Op Amps Made Easy
    Application Report SLOA099 - May 2002 Fully Differential Op Amps Made Easy Bruce Carter High Performance Linear ABSTRACT Fully differential op amps may be unfamiliar to some designers. This application report gives designers the essential information to get a fully differential design up and running. Contents 1 Introduction . 2 2 What Does Fully Differential Mean?. 2 3 How Is the Second Output Used?. 3 3.1 Differential Gain Stages. 3 3.2 Single-Ended to Differential Conversion. 4 3.3 Working With Terminated Inputs. 5 4 A New Function . 7 5 Conclusions . 8 6 References . 9 List of Figures 1 Single-Ended Op Amp Schematic Symbol. 2 2 Fully Differential Op Amp Schematic Symbol. 2 3 Closing the Loop on a Single-Ended Op Amp. 3 4 Closing the Loop on a Fully Differential Op Amp. 3 5 Single Ended to Differential Conversion. 4 6 Relationship Between Vin, Vout+, and Vout– . 5 7 Fully Differential Amplifier Component Calculator. 6 8 Using a Fully Differential Op Amp to Drive an ADC. 7 9 Effect of Vocm on Vout+ and Vout– . 8 1 SLOA099 1 Introduction Fully differential op amps may be intimidating to some designers, But op amps began as fully differential components over 50 years ago. Techniques about how to use the fully differential versions have been almost lost over the decades. However, today’s fully differential op amps offer performance advantages unheard of in those first units. This report does not attempt a detailed analysis of op amp theory; reference 1 covers theory well. Instead, this report presents just the facts a designer needs to get started, and some resources for further design assistance.
    [Show full text]
  • The Differential Amplifier
    The Differential amplifier - An Intuitive Look We will now take a look at a very versatile amplifier circuit called the differential amplifier. This amplifier is at the heart of many analog integrated circuits. We will look at the circuit only close enough to get a good intuitive feel for how it works and what it can do. Vcc rc1 rc2 1K 1K Q1 Q2 rb1 Vc1 Vc2 rb2 + + Vin1 Vin2 - - 5mA The Differential Amplifier The differential amplifier operates by amplifying the difference between two separate inputs. These inputs are marked above as Vin1 and Vin2. Note that the amplifier is symmetrical about a center line going through the 5ma current source. For the sake of this explanation, we will consider the 5mA current source to be “not quite” ideal. In this case, it means that the current source is only able to drive its upper terminal to zero volts when attempting to force a mini- mum of 5mA to flow to ground. However, it will never allow more than 5mA to flow no matter how much base current is forced into Q1 andQ2. To understand the operation of the amplifier, we will assume that Vin1 and Vin2 are equal in magnitude. Within the operating region for the amplifier, this will cause equal base and emit- ter currents to flow through each transistor. Since the current source will not allow more than 5mA of current to flow, the current through rc1 and rc2 will be exactly 2.5ma. This causes a potential of 2.5 volts to appear at Vc1 and Vc2.
    [Show full text]
  • High Input Resistance Circuits: DARLINGTON PAIR
    HRckts.doc 1 High Input Resistance circuits: The ideal voltage amplifier should have infinite input impedance and zero output impedance. The CC and CE with Re basic amplifiers have these properties. The Input impedance of these amplifiers is Ri = hie+(1+hfe)Re using the simplified model (assuming that hfeRe << 0.1) As Re ® ¥ this equation suggests that Ri ® ¥ . However, as Re ® ¥ the assumption hfeRe << 0.1 is no longer valid. And the more accurate equation is Ri = hie + (1+hfe)Re / (1+hoeRe) which ® hfe/hoe This is a theoretical limitation on Ri. There are other practical limitations also. 1. As Re increases the bias current causes a larger voltage drop across it. For middle of operating range VCE = VRe = VCC/2. We thus require larger impractical power supply voltage 2. In integrated circuits Re occupies chip area. Larger the value, greater is the chip area occupied, leaving less for other components. 3. Bias resistance appear in parallel with the Ri and with typical values of a few 100K the parallel combination RI is now decided by the bias resistance, and is hence lower. Solutions: The problems (1) and (2) are due to the fact that we are thinking of Re as Ohmic physical resistance. If Re is an equivalent resistance, created by a relatively smaller physical resistance in another CC circuit, this problem can be solved. (The DARLINGTON PAIR circuit). The bias resistance problem (3) may be solved by the BOOTSTRAPPING technique. DARLINGTON PAIR: The Darlington pair is a cascade of two common collector circuits as shown. With input resistance of Q2 acting as Re for Q1.Q1 thus sees a large equivalent Re, but the physical resistance producing this effect is R2 which is much smaller.
    [Show full text]
  • Module 4-5-Differential Amplifiers
    EE105 – Fall 2015 Microelectronic Devices and Circuits Module 4-­5: DifferentialAmplifiers Prof. Ming C. Wu [email protected] 511 Sutardja Dai Hall (SDH) Differential & Common Mode Signals Why Differential? • Differential circuits are much less sensitive to noises and interferences • Differential configuration enables us to bias amplifiers and connect multiple stages without using coupling or bypass capacitors • Differential amplifiers are widely used in IC’s – Excellent matching of transistors, which is critical for differential circuits – Differential circuits require more transistorsà not an issue for IC Neural Recording An array of electrodes is implanted in the motor cortex and senses extracellular signals that include firing from nearbyneurons The propagation of signals from neuron to neuron is called an Action Potential, which is analogous to a digital “pulse” Extracellular Neuronal Signals oltage V Local Field Potential (LFP) 1Hz-­300Hz;; 10µV-­1mV Action Potential “spikes” 300Hz-­ Time 10kHz 10µV-­1mV l The goal of a neural recording device is to record -­ the small amplitude neural signals and pick out the meaningful signals from the “noise”. l These signals are then decoded to create trajectories, movements, and speeds for controlling prostheses, computers, etc. 60Hz and Other Interferers 60 Hz Action Noise Potentials • In reality, the tiny signals recorded from the brain can get corrupted by numerous interferers. • Ambient 60Hz noise couples into electrical signals in and on the body • Motion can cause voltage artifacts
    [Show full text]
  • INA118 Precision, Low-Power Instrumentation Amplifier Datasheet
    Product Order Technical Tools & Support & Folder Now Documents Software Community INA118 SBOS027B –SEPTEMBER 2000–REVISED APRIL 2019 INA118 Precision, Low-Power Instrumentation Amplifier A newer version of this device is now available: INA818 1 Features 3 Description The INA118 is a low-power, general-purpose 1• A newer version of this device is now available: INA818 instrumentation amplifier offering excellent accuracy. The versatile, three op amp design and small size • Low offset voltage: 50 µV, maximum make this device an excellent choice for a wide range • Low drift: 0.5 µV/°C, maximum of applications. Current-feedback input circuitry • Low input bias current: 5 nA, maximum provides wide bandwidth, even at high gain (70 kHz at G = 100). • High CMR: 110 dB, minimum • Inputs protected to ±40 V A single external resistor sets any gain from 1 to 10000. Internal input protection can withstand up to • Wide supply range: ±1.35 to ±18 V ±40 V without damage. • Low quiescent current: 350 µA The INA118 is laser-trimmed for low offset voltage • Packages: 8-Pin plastic DIP, SO-8 (50 µV), drift (0.5 µV/°C), and high common-mode rejection (110 dB at G = 1000). The INA118 operates 2 Applications with power supplies as low as ±1.35 V, and quiescent • Bridge amplifiers current is only 350 µA, making this device an excellent choice for battery-operated systems. • Thermocouple amplifiers • RTD Sensor amplifiers The INA118 is available in 8-pin plastic DIP and SO-8 surface-mount packages, and specified for the –40°C • Medical instrumentation to +85°C temperature range.
    [Show full text]
  • Differential Amplifiers
    Differential Amplifiers EE105 - Spring 2007 General Considerations Microelectronic Devices and MOS Differential Pair Circuits Cascode Differential Amplifiers Common-Mode Rejection Differential Pair with Active Load Lecture 8 Differential Amplifiers 2 Audio Amplifier Example Small-Signal Model for Bipolar Transistor An audio amplifier is constructed above that takes on a Some examples in this chapter are explained in bipolar rectified AC voltage as its supply and amplifies an audio transistor circuits signal from a microphone. The small-signal model of a bipolar transistor is very similar to that of the MOSFET, except bipolar transistor has low input impedance at base 3 4 “Humming” Noise in Audio Amplifier Example Supply Ripple Rejection vAvvXvinr=+ vvYr= vvAvXY−= vin However, V contains a ripple from rectification that CC Since both node X and Y contain the ripple, their leaks to the output and is perceived as a “humming” difference will be free of ripple. noise by the user. 5 6 Ripple-Free Differential Output Common Inputs to Differential Amplifier vAvvX =+vin r vAvvYvinr=+ vvXY−=0 Signals cannot be applied in phase to the inputs of a Since the signal is taken as a difference between two differential amplifier, since the outputs will also be in nodes, an amplifier that senses differential signals is phase, producing zero differential output. needed. 7 8 Differential Inputs to Differential Amplifier Differential Signals vAvvXvinr=+ vAvvYvinr=− + vvXY−=2 Av vin A pair of differential signals can be generated, among other ways, by a transformer. When the inputs are applied differentially, the outputs Differential signals have the property that they share the are 180° out of phase; enhancing each other when same average value to ground and are equal in sensed differentially.
    [Show full text]