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Application Notes

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  An Introduction to Acoustic Thermometry &mdash AN131
  PDF, 456 Kb, File published: Apr 26, 2011
  Acoustic thermometry is an arcane, elegant temperature measurement technique. It utilizes sound's temperature dependent transit time in a medium to measure temperature. The medium may be a solid, liquid or gas. Acoustic thermometers function in environments that conventional sensors cannot tolerate. Examples include extreme temperatures, applications where the sensor would be subjected to destructive physical abuse and nuclear reactors. This application note describes theory, practical acoustic thermometer circuitry and transducer construction details. Two appended sections cover calibration and present a complete software listing.
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  Application Note 131
  February 2011
  An Introduction to Acoustic Thermometry
  An Air Filled Olive Jar Teaches Signal Conditioning
  Jim Williams and Omar Sanchez-Felipe
  Introduction
  We occasionally lecture to university engineering students.
  A goal of these lectures is to present technology in a novel,
  even charming, way. This hopefully entices the student
  towards the topic; an aroused curiosity is fertile ground
  for education. One such lecture investigates acoustic thermometry as an example of signal conditioning techniques.
  This subject has drawn enough interest that it is presented
  here for wider dissemination and as supplementary material for future acoustic thermometry lectures.
  Acoustic Thermometry
  Acoustic thermometry is an arcane, elegant temperature
  measurement technique. It utilizes sound’s temperature
  dependent transit time in a medium to measure temperature. The medium may be a solid, liquid or gas. Acoustic
  thermometers function in environments that conventional
  sensors cannot tolerate. Examples include extreme temperatures, applications where the sensor would be subjected to destructive physical abuse and nuclear reactors.
  Gas path acoustic thermometers respond very quickly to
  temperature changes because they have essentially no
  thermal mass or lag. An acoustic thermometer’s “body” is the measurand. Additionally, an acoustic thermometer’s
  reported “temperature” represents the total measurement …

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  High Speed Amplifier Techniques &mdash AN47
  PDF, 5.3 Mb, File published: Aug 1, 1991
  This application note, subtitled "A Designer's Companion for Wideband Circuitry," is intended as a reference source for designing with fast amplifiers. Approximately 150 pages and 300 figures cover frequently encountered problems and their possible causes. Circuits include a wide range of amplifiers, filters, oscillators, data converters and signal conditioners. Eleven appended sections discuss related topics including oscilloscopes, probe selection, measurement and equipment considerations, and breadboarding techniques.
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  Application Note 47
  August 1991
  High Speed Amplifier Techniques
  A Designer’s Companion for Wideband Circuitry
  Jim Williams PREFACE
  This publication represents the largest LTC commitment
  to an application note to date. No other application note
  absorbed as much effort, took so long or cost so much.
  This level of activity is justified by our belief that high speed
  monolithic amplifiers greatly interest users.
  Historically, monolithic amplifiers have represented packets of inexpensive, precise and controllable gain. They
  have partially freed engineers from the constraints and
  frustrations of device level design. Monolithic operational
  amplifiers have been the key to practical implementation
  of high level analog functions. As good as they are, one
  missing element in these devices has been speed.
  Devices presently coming to market are addressing monolithic amplifiers’ lack of speed. They bring with them the
  ease of use and inherent flexibility of op amps. When Philbrick Researches introduced the first mass produced
  op amp in the 1950’s (K2-W) they knew it would be used.
  What they couldn’t possibly know was just how widely,
  and how many different types of applications there were.
  As good a deal as the K2-W was (I paid $24.00 for mine or rather, my father did), monolithic devices are far better.
  The combination of ease of use, economy, precision and …

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  Video Circuit Collection &mdash AN57
  PDF, 559 Kb, File published: Jan 2, 1994
  AN57, the Video Circuit Collection, features a variety of video circuits designed at LTC. The LT1204 70MHz multiplexer is featured in a number of circuits which require excellent video isolation from channel to channel. High speed voltage and current feedback amplifiers are highlighted throughout the section on video processing circuits. There is a section on applying Current Feedback Amplifiers (CFAs) and a number of articles taken from the Linear Technology magazine.
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  Application Note 57
  January 1994
  Video Circuit Collection
  Jon Munson and Frank Cox
  INTRODUCTION
  Even in a time of rapidly advancing digital image processing, analog video signal processing still remains eminently
  viable. The video A/D converters need a supply of properly
  amplified, limited, DC restored, clamped, clipped, contoured, multiplexed, faded and filtered analog video before
  they can accomplish anything. After the digital magic is
  performed, there is usually more amplifying and п¬Ѓltering
  to do as an adjunct to the D/A conversion process, not to mention all those pesky cables to drive. The analog way
  is often the most expedient and efficient, and you don’t
  have to write all that code.
  The foregoing is only partly in jest. The experienced engineer
  will use whatever method will properly get the job done;
  analog, digital or magic (more realistically, a combination
  of all three). Presented here is a collection of analog video
  circuits that have proven themselves useful. CIRCUIT INDEX
  I. Video Amplifier Selection Guide . 2 II. Video Cable Drivers . 3
  AC-Coupled Video Drivers . 3
  DC-Coupled Video Drivers . 4
  Clamped AC-Input Video Cable Driver . 5
  Twisted-Pair Video Driver and Receiver . 5 III. Video Processing Circuits . 6 …

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  Component and Measurement Advances Ensure 16-Bit DAC Settling Time &mdash AN74
  PDF, 980 Kb, File published: Jul 1, 1998
  DAC DC specifications are relatively easy to verify. AC specifications require more sophisticated approaches to produce reliable information. In particular, the settling time of the DAC and its output amplifier is extraordinarily difficult to determine to 16-bit resolution. This application note presents methods for 16-bit DAC settling time measurement and compares results. Appendices discuss oscilloscope overdrive, frequency compensation, circuit and optimization techniques, layout, power stages and a historical perspective of precision DACs.
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  Application Note 74
  July 1998
  Component and Measurement Advances Ensure
  16-Bit DAC Settling Time
  The art of timely accuracy
  Jim Williams
  Introduction
  Instrumentation, waveform generation, data acquisition,
  feedback control systems and other application areas are
  beginning to utilize 16-bit data converters. More specifically, 16-bit digital-to-analog converters (DACs) have
  seen increasing use. New components (see Components
  for 16-Bit Digital-to-Analog Conversion, page 2) have
  made 16-bit DACs a practical design alternative1. These
  ICs provide 16-bit performance at reasonable cost compared to previous modular and hybrid technologies. The
  DC and AC specifications of the monolithic DAC’s
  approach or equal previous converters at significantly
  lower cost.
  DAC Settling Time
  DAC DC specifications are relatively easy to verify. Measurement techniques are well understood, albeit often
  tedious. AC specifications require more sophisticated
  approaches to produce reliable information. In particular,
  the settling time of the DAC and its output amplifier is
  extraordinarily difficult to determine to 16-bit resolution. …

Design Notes

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  C-Load TM Op Amps Conquer Instabilities &mdash DN107
  PDF, 495 Kb, File published: Jul 1, 1995
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  C-Load Op Amps Conquer Instabilities – Design Note 107
  Kevin R. Hoskins
  Introduction
  Linear Technology Corporation has taken advantage of
  advances in process technology and circuit innovations
  to create a series of C-Loadв„ў operational amplifiers that
  are tolerant of capacitive loading, including the ultimate,
  amplifiers that remain stable driving any capacitive load.
  This series of amplifiers has a bandwidth that ranges from
  160kHz to 140MHz. These amplifiers are appropriate for
  a wide range of applications from coaxial cable drivers to
  analog-to-digital converter (ADC) input buffer/amplifiers.
  Driving ADCs
  Most contemporary ADCs incorporate a sample-and-hold
  (S/H). A typical S/H circuit is shown in Figure 1. The hold
  capacitor’s (C1) size varies with the ADC’s resolution but
  is generally in the range of 5pF to 20pF, 10pF to 30pF and
  10pF to 50pF for 8-, 10-and 12-bit ADCs, respectively. gracefully and accurately drive capacitive loads, such as
  Linear Technology’s C-Load line of monolithic amplifiers.
  Table 1 lists Linear Technology’s unconditionally stable
  voltage feedback C-Load amplifiers. Table 2 lists other
  voltage feedback C-Load amplifiers that are stable with
  loads up to 10,000pF. …

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  Updated Operational Amplifier Selection Guide for Optimum Noise Performance &mdash DN140
  PDF, 74 Kb, File published: Oct 1, 1996
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  Operational Amplifier Selection Guide for
  Optimum Noise Performance – Design Note 140
  Frank Cox
  Eight years ago, George Erdi wrote a very useful Design
  Note (DN6) that presented information to aid in the
  selection of op amps for optimum noise performance,
  in both graphical and tabular form. Design Note 140 is
  an update of DN6. It covers new low noise op amps as
  well as some high speed op amps. Although a great deal
  has changed in eight years, especially in electronics,
  noise is still a critical issue in op amp circuit design
  and the LTВ®1028 is still the lowest noise op amp for
  low source impedance applications.
  The amount of noise an op amp circuit will produce
  is determined by the device used, the total resistance
  in the circuit, the bandwidth of the measurement, the
  temperature of the circuit and the gain of the circuit. A
  convenient п¬Ѓgure of merit for the noise performance
  of an op amp is the spectral density or spot noise. This
  is obtained by normalizing the measurement to a unit
  of bandwidth. Here the unit is 1Hz and the noise is reported as “nV/√Hz.” The noise in a particular application
  bandwidth can be calculated by multiplying the spot
  noise by the square root of the application bandwidth. …

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  Current Feedback Amplifier Do's and Don'ts &mdash DN46
  PDF, 167 Kb, File published: Apr 1, 1991
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  Current Feedback Amplifier “Do’s and Don’ts” – Design Note 46
  William H. Gross
  Introduction
  The introduction of current feedback amplifiers, such as
  the LT®1223, has significantly increased the designer’s
  ability to solve difficult high speed amplifier problems.
  The current feedback architecture has very high slew rate
  and the small-signal bandwidth is fairly constant for all
  gains. Current feedback amplifiers are used in broadcast
  video systems, radar systems, IF and RF stages, RGB
  distribution systems and many other high speed circuits.
  As with any new circuit, there are several new rules that
  must be kept in mind to prevent problems. Because current
  feedback amplifiers act very much the same as regular op
  amps, it is important to note the differences and show how
  some standard op amp circuits should be implemented.
  The most important thing to remember about current
  feedback amplifiers is that the impedance at the inverting (negative) input sets the bandwidth and therefore the
  stability of the amplifier. It should be resistive, not capacitive. To slow the amplifier down, increase the resistance
  driving the inverting input. If the amplifier peaks too much
  due to capacitive loading or anything else, increase the
  value of the feedback resistors.
  The best way to demonstrate how to use current feedback …

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  High Frequency Amplifier Evaluation Board &mdash DN50
  PDF, 121 Kb, File published: Jan 1, 1991
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  High Frequency Amplifier Evaluation Board – Design Note 50
  Mitchell Lee
  Introduction
  Demo board DC009 is designed to simplify the evaluation
  of high speed operational amplifiers. It includes both an
  inverting and non-inverting circuit, and pads are provided
  to allow the use of board-mounted BNC or SMA connectors.
  The two circuits are independent, with the exception of
  shared power supply and ground connections. High Speed Layout Techniques grounds are still separated. For example, the termination
  resistors (R3 and R7) and the gain-setting resistor (R1)
  are grounded in the vicinity of the input connector. Supply
  bypass capacitors (C1, C2, C4, C5, C7, C8, C9, and C10)
  are returned to ground in the vicinity of the output
  connectors. Optional Components Layout is a primary contributor to the performance of any
  high speed amplifier. Poor layout techniques adversely
  affect the behavior of a finished circuit. Several important
  layout techniques, all used in demo board DC009, are
  described below: The circuit board is designed to accommodate standard 8pin miniDIP, single operational amplifiers, such as the
  LT1190 and LT1220 families. Both voltage and current
  feedback types can be used. Pins 1, 5, and 8 are outfitted
  with pads for use in adjusting DC offsets, compensation
  or, in the case of the LT1223 and LT1190/1/2, for shutting
  down the amplifier. Top Side Ground Plane: The primary task of a ground …

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  C-Load TM Op Amps Tame Instabilities &mdash DN83
  PDF, 929 Kb, File published: Jun 1, 1994
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  C-Load Op Amps Tame Instabilities – Design Note 83
  Richard Markell, George Feliz and William Jett
  Introduction
  By taking advantage of advances in process technology
  and innovative circuit design, Linear Technology Corporation has developed a series of C-Loadв„ў op amps which
  are tolerant of capacitive loading, including the ultimate,
  amplifiers which are stable with any capacitive load. These
  amplifiers span a range of bandwidths from 1MHz to
  140MHz. They are suited for a wide range of applications
  from coaxial cable drivers to capacitive transducer exciters.
  The Problem
  The cause of the capacitive load stability problem in most
  amplifiers is the pole formed by the load capacitance and
  the open-loop output impedance of the amplifier. This
  output pole increases the phase lag around the loop which
  reduces the phase margin of the amplifier. If the phase
  lag is great enough the amplifier will oscillate.
  External networks can be used to improve the amplifier’s
  stability with a capacitive load but have serious drawbacks.
  For instance, most designers are familiar with the use of
  a series resistor RS between the load and the amplifier
  output. The optimum value of RS depends on the load
  capacitance, so this approach isn’t useful for ill-defined …

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Manufacturer's Classification

• Signal Conditioning > Amplifiers > Operational Amplifiers (Op Amps) > General Purpose Amplifiers | High Voltage Amplifiers (>12V)