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Application Notes

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  Thermocouple Measurement &mdash AN28
  PDF, 988 Kb, File published: Feb 1, 1988
  Considerations for thermocouple-based temperature measurement are discussed. A tutorial on temperature sensors summarizes performance of various types, establishing a perspective on thermocouples. Thermocouples are then focused on. Included are sections covering cold-junction compensation, amplifier selection, differential/isolation techniques, protection, and linearization. Complete schematics are given for all circuits. Processor- based linearization is also presented with the necessary software detailed.
  Extract from the document

  Application Note 28
  February 1988
  Thermocouple Measurement
  Jim Williams
  Introduction Thermocouples in Perspective In 1822, Thomas Seebeck, an Estonian physician, accidentally joined semicircular pieces of bismuth and copper
  (Figure 1) while studying thermal effects on galvanic arrangements. A nearby compass indicated a magnetic disturbance. Seebeck experimented repeatedly with different
  metal combinations at various temperatures, noting relative
  magnetic п¬Ѓeld strengths. Curiously, he did not believe that
  electric current was flowing, and preferred to describe the
  effect as “thermo-magnetism.” He published his results in
  a paper, “Magnetische Polarisation der Metalle und Erze
  durch Temperatur-Differenz” (see references). Temperature is easily the most commonly measured
  physical parameter. A number of transducers serve temperature measuring needs and each has advantages and
  considerations. Before discussing thermocouple-based
  measurement it is worthwhile putting these sensors in
  perspective. Figure 2’s chart shows some common contact
  temperature sensors and lists characteristics. Study reveals
  thermocouple strengths and weaknesses compared to
  other sensors. In general, thermocouples are inexpensive,
  wide range sensors. Their small size makes them fast and
  their low output impedance is a benefit. The inherent voltage output eliminates the need for excitation. Subsequent investigation has shown the “Seebeck Effect”
  to be fundamentally electrical in nature, repeatable, and
  quite useful. Thermocouples, by far the most common …

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  Measurement and Control Circuit Collection &mdash AN45
  PDF, 1.2 Mb, File published: Jun 5, 1991
  A variety of measurement and control circuits are included in this application note. Eighteen circuits, including ultra low noise amplifiers, current sources, transducer signal conditioners, oscillators, data converters and power supplies are presented. The circuits emphasize precision specifications with relatively simple configurations.
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  Application Note 45
  June 1991
  Measurement and Control Circuit Collection
  Diapers and Designs on the Night Shift
  Jim Williams
  Introduction
  During my wife’s pregnancy I wondered what it would
  really be like when the baby was finally born. Before that
  time, there just wasn’t much mothering and fathering to
  do. As a consolation, we busied ourselves watching the
  baby’s heartbeat (Figure 1) on a thrown-together fetal heart
  monitor (see References). feedings. As such, the circuits are annotated with the
  number of feedings required for their completion; e.g., a
  “3-bottle circuit” took three feedings. The circuit’s degree
  of difficulty, and Michael’s degree of cooperation, combined
  to determine the bottle rating, which is duly recorded in
  each figure.
  Low Noise and Drift Chopped Bipolar Amplifier
  Figure 2’s circuit combines the low noise of an LT®1028
  with a chopper based carrier modulation scheme to achieve
  an extraordinarily low noise, low drift DC amplifier. DC
  drift and noise performance exceed any currently available
  monolithic amplifier. Offset is inside 1ОјV, with drift less …

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  Applications of the LT1300 and LT1301 Micropower DC/DC Converters &mdash AN59
  PDF, 213 Kb, File published: Jan 1, 1994
  This note covers operation and applications of the LT1300 and LT1301 high efficiency micropower step-up DC/DC converter ICs. Internal operation of the ICs is described in detail. A variety of applications are presented, ranging from straightforward 2-cell to 5V converters and 5V to 12V converters to exotic transducerbased circuits such as flame detectors and CCFL drivers. Converters from both 2-cell and 4-cell inputs are included. Operating hours at various load currents are presented and relative merits of different battery types are discussed.
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  Application Note 59
  January 1994
  Applications of the LT1300 and LT1301
  Micropower DC/DC Converters
  Dale Eagar and Steve Pietkiewicz
  INTRODUCTION
  The design of battery-powered equipment can often be
  quite challenging. Since few ICs can operate directly from
  the end-of-life voltage from a 2-cell battery (about 1.8V),
  most systems require a DC/DC converter. The system
  designer often has a limited area in which to place the DC/
  DC converter; associated inductors and capacitors must be
  small. Surface mount components are a must and heat
  sinks are out of the question! The LT1300 and LT1301
  micropower DC/DC converter ICs provide new possibilities
  for more efficient, compact and cost effective designs.
  When designing equipment for battery-powered
  operation, a number of important design constraints
  should be considered. Some of these are detailed in the
  check list given here: Design for high efficiency. A high efficiency converter
  increases battery life, eliminates most heat sinks, reduces
  weight and decreases PC board area. The designer
  should strive for high efficiency at: …

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  Linear Technology Magazine Circuit Collection, Volume III &mdash AN67
  PDF, 1.2 Mb, File published: Sep 1, 1996
  Application Note 67 is a collection of circuits for data conversion, interface and signal processing from the first five years of Linear Technology. This application note includes circuits such as fast video multiplexers for high speed video, an ultraselective bandpass filter circuit with adjustable gain, and a fully differential, 8-channel, 12-bit A/D system. The categories included in this app note are data conversion, interface, filters, instrumentation, video/op amps and miscellaneous circuits.
  Extract from the document

  Application Note 67
  September 1996
  Linear Technology Magazine Circuit Collection, Volume III
  Data Conversion, Interface and Signal Processing
  Richard Markell, Editor
  INTRODUCTION
  Application Note 67 is a collection of circuits from the first
  five years of Linear Technology, targeting data conversion,
  interface and signal processing applications. This
  Application Note includes circuits such as fast video
  multiplexers for high speed video, an ultraselective
  bandpass filter circuit with adjustable gain and a fully differential, 8-channel, 12-bit A/D system. The categories
  included herein are data conversion, interface, filters,
  instrumentation, video/op amps and miscellaneous
  circuits. Application Note 66, which covers power products
  and circuits from Linear Technology ’s first five years, is
  also available from LTC. ARTICLE INDEX
  Data Conversion . 3
  Fully Differential, 8-Channel, 12-Bit A/D System Using the LTCВ®1390 and LTC1410 . 3
  12-Bit DAC Applications . 5
  LTC1329 Micropower, 8-Bit, Current Output DAC Used for Power Supply Adjustment,
  Trimmer Pot Replacement . 7
  12-Bit Cold Junction Compensated, Temperature Control System with Shutdown . 8 …

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  A Seven-Nanosecond Comparator for Single Supply Operation &mdash AN72
  PDF, 882 Kb, File published: May 1, 1998
  AN72 is an extensive discussion of the causes and cures of problems in very high speed comparator circuits. A separate applications section uses the 7ns LT1394 in V-to-F converters, crystal oscillators, clock skew generators, triggers, sampling configurations and a nanosecond pulse stretcher. Appendices cover related topics.
  Extract from the document

  Application Note 72
  May 1998
  A Seven-Nanosecond Comparator
  for Single Supply Operation
  Guidance for Putting Civilized Speed to Work
  Jim Williams INTRODUCTION
  In 1985 Linear Technology Corporation introduced the
  LT В®1016 Comparator. This device was the first readily
  usable, high speed TTL comparator. Previous ICs were
  either too slow or unstable, preventing widespread
  acceptance. The LT1016 was, and is, a highly successful
  product.
  Recent technology trends have emphasized low power,
  single supply operation. The LT1016, although capable of
  such operation, does not include ground in its input range.
  As such, it must be biased into its operating common
  mode range for practical single supply use. A new device,
  the LT1394, maintains the speed and application civility of
  its predecessor while including ground in its input operating range. Additionally, the new comparator is faster and
  pulls significantly lower operating current than the LT1016.
  This publication borrows shamelessly from earlier LTC
  efforts, while introducing new material.1 It approximates,
  affixes, appends, abridges, amends, abbreviates, abrogates, ameliorates and augments the previous work.2 …

Design Notes

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  A Precision Wideband Current Probe for LCD Backlight Measurement &mdash DN101
  PDF, 93 Kb, File published: Apr 1, 1995
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  A Precision Wideband Current Probe for LCD Backlight
  Measurement – Design Note 101
  Jim Williams
  Evaluation and optimization of Cold Cathode Fluorescent
  Lamp (CCFL) performance requires highly accurate
  AC current measurement. CCFLs, used to backlight
  LCD displays, typically operate at 30kHz to 70kHz
  with measurable harmonic content into the low MHz
  region1. Accurate determination of RMS operating current is important for electrical and emissivity efficiency
  computations and to ensure long lamp life. Additionally,
  it is desirable to be able to perform current measurements in the presence of high common-mode voltage
  (>1000VRMS). This capability allows investigation and
  quantification of display and wiring induced losses,
  regardless of their origins in the lamp drive circuitry. operating at a gain of about 3.75. No impedance matching is required due to the probe’s low output impedance
  termination. Additional amplifiers provide distributed
  gain, maintaining wide bandwidth with an overall gain
  of about 200. The individual amplifiers avoid any possible crosstalk-based error that could be introduced
  by a monolithic quad amplifier. D1 and Rx are selected
  for polarity and value to trim overall amplifier offset.
  The 100О© trimmer sets gain, п¬Ѓxing the scale factor.
  The output drives a thermally-based, wideband RMS
  voltmeter. In practice, the circuit is built into a 2.25" Г—
  1" Г— 1" enclosure which is directly connected, via BNC …

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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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  Chopper vs Bipolar Op Amps—An Unbiased Comparison &mdash DN42
  PDF, 70 Kb, File published: Dec 1, 1990
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  Chopper vs Bipolar Op Amps—An Unbiased Comparison
  Design Note 42
  George Erdi Table 1 lists the parameters of importance. In all input
  parameters (except noise) the advantage unquestionably goes to the choppers. 5ОјV maximum offset voltage, 0.5ОјV/В°C maximum drift are commonly found
  Table 1. Chopper Stabilized vs Precision Bipolar Op Amps
  ADVANTAGE
  PARAMETER
  Offset Voltage
  Offset Drift
  All Other DC Specs CHOPPER BIPOLAR COMMENTS
  вњ“
  вњ“
  вњ“ No Contest Wideband, 20Hz to
  1MHz вњ“ See Details in Text Noise вњ“ See Details in Text вњ“ Rail to Rail Swing
  2mA Limit on
  Choppers Output: Light Load
  Heavy Load
  Single Supply
  Application вњ“ вњ“ Inherent to
  Choppers Needs
  Special Design
  Bipolars В±15V Supply Voltage вњ“ Except LTC1150 Prejudice/Tradition вњ“ Still a Chopper
  Problem Cost 08/90/86_conv вњ“ Unless DC …

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  Gain Trimming In Instrumentation Amplifier Based Systems &mdash DN51
  PDF, 78 Kb, File published: Jun 1, 1991
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  Gain Trimming In Instrumentation Amplifier
  Based Systems – Design Note 51
  Jim Williams
  Gain trimming is almost always required in instrumentation amplifier based systems. Gain uncertainties, most
  notable in transducers, necessitate such a trim.
  Figure 1, a conceptual system, shows several points as
  candidates for the trim. In practice, only one of these
  must actually be used. The appropriate trim location
  varies with the individual application.
  Figure 2 approaches gain trimming by altering transducer excitation. The gain trim adjustment results in
  changes in the LT®1010’s output. The LT1027 reference
  and LT1097 ensure output stability. Transducer output varies with excitation, making this a viable approach.
  It is important to consider that gain “lost” by reducing
  transducer drive translates into reduced signal-to-noise
  ratio. As such, gain reduction by this method is usually
  limited to small trims, e.g., 5-10%. Similarly, too much
  gain introduced by this method can cause excessive
  transducer drive, degrading accuracy. The transducer
  manufacturer’s data sheet should list the maximum
  permissible drive for rated accuracy.
  L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks
  of Linear Technology Corporation. All other trademarks are the property of their
  respective owners. &9$*5"5*0/ …

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  3V Operation of Linear Technology Op Amps &mdash DN56
  PDF, 78 Kb, File published: Feb 1, 1992
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  3V Operation of Linear Technology Op Amps -Design Note 56
  George Erdi
  The latest trend in digital electronics is the introduction
  of numerous ICs operating on regulated 3V or 3.3V
  power supplies. This is a logical development to increase
  circuit densities and to reduce power dissipation. In addition, many systems are directly powered by two AA
  cells or 3V lithium batteries. Clearly, analog ICs which
  work on 3V with good dynamic range to complement
  these digital circuits are, and will be, in great demand.
  Many Linear Technology operational amplifiers work
  well on a 3V supply. The purpose of this design note
  is to list these devices and their performance when
  powered by 3V. The op amps can be divided into two
  groups: single and dual supply devices. The single supply
  op amps are optimized for, and fully specified at, a 5V
  positive supply with the negative supply terminal tied
  to ground. Input common mode voltage range goes
  below ground, and the output swings to within a few
  millivolts of ground while sinking current. Members of
  the single supply family are the micropower LTВ®1077/
  LT1078/LT1079 single, dual and quad op amps with
  40μA supply current per amplifier, the LT1178/LT1179 dual and quad with 13μA per amplifier. The LT1006/
  LT1013/LT1014 single, dual and quad have faster speed …

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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 …

Articles

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  New Instrumentation Amplifier: Single-Resistor Gain Set and Precision Front End Make Accuracy Easy &mdash LT Journal
  PDF, 159 Kb, File published: May 1, 2000
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  DESIGN FEATURES New Instrumentation Amplifier: SingleResistor Gain Set and Precision Front
  End Make Accuracy Easy
  by Glen Brisebois
  The LT1168 is a low power,
  single-resistor gain-programmable
  instrumentation amplifier that is easy
  to apply. It is a pin-compatible upgrade
  for the AD620 (and the INA118 with a
  resistor-value change) and is available in C and I grades. With negligible
  60µV (Max) offset voltage and ultrahigh 1TΩ input impedance, it can
  sense bridges with source impedances
  from 10Ω to 100k without degrading
  the signal. Its 120dB CMRR at 60Hz
  (AV = 100V) is achieved even with a 1k
  source impedance imbalance. Matching the LT1168’s CMRR using discrete
  op amps would require the use of
  0.001% resistors. The LT1168’s
  robust inputs meet IEC1000-4-2
  Level 4 ESD tests with the addition of
  two external 5k series resistors. These
  5k resistors will contribute only a
  negligible 6ВµV of DC error. Table 1. Examples of series resistors for precision gain Desired Gain RG
  (Theoretical) RG1 …

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  Consider New Precision Amplifiers for Updated Industrial Equipment Designs &mdash LT Journal
  PDF, 154 Kb, File published: Sep 1, 2009
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  L DESIGN FEATURES Consider New Precision Amplifiers for
  Updated Industrial Equipment Designs
  by Brian Black Introduction
  Industrial equipment is designed for
  long life cycles, so the electronic components used in industrial applications
  are often chosen with significant emphasis on proven performance, quality
  and reliability. Precision amplifiers are
  no exception. Even if new and innovative amplifiers become available over a
  product’s lifetime, a redesigned board
  is often built using the same proven
  op amps in the old board. Even for
  entirely new applications, designers
  will choose amplifiers that have proven
  their mettle in other circuits, making a
  choice based more on familiarity than
  performance.
  Although an amplifier may have
  been tried and proven in a design, it
  is not necessarily the best solution for
  every new design. Many can benefit
  from using more recently released
  amplifiers, which can improve overall
  system performance, reduce power …

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Manufacturer's Classification

• Signal Conditioning > Amplifiers > Operational Amplifiers (Op Amps) > Precision Amplifiers (Vos | High Voltage Amplifiers (>12V) | Low Power Amplifiers (Is < 1mA/amp) | Low Bias Current Amplifiers (Ib < 100pA)