Mikropower-Spannungsreferenz
PDF, 230 Kb, Datei veröffentlicht: Sep 1, 1985
This note covers the considerations for designing precision linear circuits which must operate from a single 5V supply. Applications include various transducer signal conditioners, instrumentation amplifiers, controllers and isolated data converters.
Auszug aus dem Dokument
Application Note 11
September 1985
Designing Linear Circuits for 5V Single Supply Operation
Jim Williams
In predominantly digital systems it is often necessary
to include linear circuit functions. Traditionally, separate
power supplies have been used to run the linear components (see Box, “Linear Power Supplies—Past, Present,
and Future”).
Recently, there has been increasing interest in powering
linear circuits directly from the 5V logic rail. The logic
rail is a difficult place for analog components to function.
The high amplitude broadband current and voltage noise
generated by logic clocking makes analog circuit operation difficult. (See Box, “Using Logic Supplies for Linear
Functions”.)
Generally speaking, analog circuitry which must achieve
very high performance levels should be driven from dedicated supplies. The difficulties encountered in maintaining
the lowest possible levels of noise and drift in an analog
system are challenging enough without contending with
a digitally corrupted power supply.
Many analog applications, however, can be successfully
implemented using the logic supply. Combining components intended to provide high performance from the 167Ω Q1 –
+ 2M 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. RATIOMETRIC …
PDF, 1.1 Mb, Datei veröffentlicht: Apr 1, 1985
The AN13 is an extensive discussion of the causes and cures of problems in very high speed comparator circuits. A separate applications section presents circuits, including a 0.025% accurate 1Hz to 30MHz V/F converter, a 200ns 0.01% sample-hold and a 10MHz fiber-optic receiver. Five appendices covering related topics complete this note.
Auszug aus dem Dokument
Application Note 13
April 1985
High Speed Comparator Techniques
Jim Williams
INTRODUCTION
Comparators may be the most underrated and underutilized monolithic linear component. This is unfortunate
because comparators are one of the most flexible and
universally applicable components available. In large
measure the lack of recognition is due to the IC op amp,
whose versatility allows it to dominate the analog design
world. Comparators are frequently perceived as devices,
which crudely express analog signals in digital form—a
1-bit A/D converter. Strictly speaking, this viewpoint is
correct. It is also wastefully constrictive in its outlook.
Comparators don’t “just compare” in the same way that
op amps don’t “just amplify”.
Comparators, in particular high speed comparators, can
be used to implement linear circuit functions which are
as sophisticated as any op amp-based circuit. Judiciously
combining a fast comparator with op amps is a key to
achieving high performance results. In general, op ampbased circuits capitalize on their ability to close a feedback
loop with precision. Ideally, such loops are maintained
continuously over time. Conversely, comparator circuits …
PDF, 387 Kb, Datei veröffentlicht: Mar 1, 1986
A variety of high performance V/F circuits is presented. Included are a 1Hz to 100MHz design, a quartz-stabilized type and a 0.0007% linear unit. Other circuits feature 1.5V operation, sine wave output an nonlinear transfer functions. A separate section examines the trade-offs and advantages of various approaches to V/F conversion.
Auszug aus dem Dokument
Application Note 14
March 1986
Designs for High Performance Voltage-to-Frequency
Converters
Jim Williams
Monolithic, modular and hybrid technologies have been
used to implement voltage-to-frequency converters. A
number of types are commercially available and overall
performance is adequate to meet many requirements. In
many cases, however, very high performance or special
characteristics are required and available units will not work.
In these instances V→F circuits specifically optimized for
the desired parameters(s) are required. This application
note presents examples of circuits which offer substantially improved performance over commercially available
V→Fs. Various approaches (see Box Section, “V→F
Design Techniques”) permit improvements in speed, dynamic range, stability and linearity. Other circuits feature
low voltage operation, sine wave output and deliberate
nonlinear transfer functions.
Ultra-High Speed 1Hz to 100MHz V→F Converter
Figure 1’s circuit uses a variety of circuit methods to
achieve wider dynamic range and higher speed than any
commercial V→F. Rocketing along at 100MHz full-scale
(10% overrange to 110MHz is provided), it leaves all other …
PDF, 195 Kb, Datei veröffentlicht: Nov 1, 1985
1.5V powered circuits for complex linear functions are detailed. Designs include a V/F converter, a 10-bit A/D, sample-hold amplifiers, a switching regulator and other circuits. Also included is a section of component considerations for 1.5V powered linear circuits.
Auszug aus dem Dokument
Application Note 15
November 1985
Circuitry for Single Cell Operation
Jim Williams
Portable, battery-powered operation of electronic apparatus has become increasingly desirable. Medical, remote
data acquisition, power monitoring and other applications
are good candidates for battery operation. In some circumstances, due to space, power or reliability considerations,
it is preferable to operate the circuitry from a single 1.5V
cell. Unfortunately, a 1.5V supply eliminates almost all
linear ICs as design candidates. In fact, the LM10 op
amp-reference and the LTВ®1017/LT1018 comparators are
the only IC gain blocks fully specified for 1.5V operation.
Further complications are presented by the 600mV drop
of silicon transistors and diodes. This limitation consumes
a substantial portion of available supply range, making
circuit design difficult. Additionally, any circuit designed
for 1.5V operation must function at end-of-life battery
voltage, typically 1.3V. (See Box Section, “Components
for 1.5V Operation.”)
500k
10kHz
TRIM
EIN …
PDF, 3.3 Mb, Datei veröffentlicht: Sep 1, 1987
AN22 details the theoretical and application aspects of the LT1088 thermal RMS/DC converter. The basic theory behind thermal RMS/DC conversion is discussed and design details of the LT1088 are presented. Circuitry for RMS/DC converters, wideband input buffers and heater protection is shown.
PDF, 2.2 Mb, Datei veröffentlicht: Apr 1, 1987
Low power operation of electronic apparatus has become increasingly desirable. AN23 describes a variety of low power circuits for transducer signal conditioning. Also included are designs for data converters and switching regulators. Three appended sections discuss guidelines for micropower design, strobed power operation and effects of test equipment on micropower circuits.
Auszug aus dem Dokument
Application Note 23
April 1987
Micropower Circuits for Signal Conditioning
Jim Williams
Low power operation of electronic apparatus has become
increasingly desirable. Medical, remote data acquisition,
power monitoring and other applications are good candidates for battery driven, low power operation. Micropower
analog circuits for transducer-based signal conditioning
present a special class of problems. Although micropower
ICs are available, the interconnection of these devices to
form a functioning micropower circuit requires care. (See
Box Sections, “Some Guidelines for Micropower Design
and an Example” and “Parasitic Effects of Test Equipment
on Micropower Circuits.”) In particular, trade-offs between
signal levels and power dissipation become painful when
performance in the 10-bit to 12-bit area is desirable. Additionally, many transducers and analog signals produce +V inherently small outputs, making micropower requirements complicate an already difficult situation. Despite the
problems, design of such circuits is possible by combining
high performance micropower ICs with appropriate circuit
techniques.
Platinum RTD Signal Conditioner
Figure 1 shows a simple circuit for signal conditioning
a platinum RTD. Correction for the platinum sensor’s
nonlinear response is included. Accuracy is 0.25В°C over …
PDF, 359 Kb, Datei veröffentlicht: Sep 2, 1987
Subtitled "A Gentle Guide for the Trepidatious," this is a tutorial on switching regulator design. The text assumes no switching regulator design experience, contains no equations, and requires no inductor construction to build the circuits described. Designs detailed include flyback, isolated telecom, off-line, and others. Appended sections cover component considerations, measurement techniques and steps involved in developing a working circuit.
Auszug aus dem Dokument
Application Note 25
September 1987 Switching Regulators for Poets
A Gentle Guide for the Trepidatious
Jim Williams
The above title is not happenstance and was arrived at after
considerable deliberation. As a linear IC manufacturer, it is
our goal to encourage users to design and build switching
regulators. A problem is that while everyone agrees that
working switching regulators are a good thing, everyone
also agrees that they are difficult to get working. Switching
regulators, with their high efficiency and small size, are
increasingly desirable as overall package sizes shrink.
Unfortunately, switching regulators are also one of the
most difficult linear circuits to design. Mysterious modes,
sudden, seemingly inexplicable failures, peculiar regulation characteristics and just plain explosions are common
occurrences. Diodes conduct the wrong way. Things get
hot that shouldn’t. Capacitors act like resistors, fuses
don’t blow and transistors do. The output is at ground, and
the ground terminal shows volts of noise.
Added to this poisonous brew is the regulator’s feedback
loop, sampled in nature and replete with uncertain phase
shifts. Everything, of course, varies with line and load
conditions— and the time of day, or so it seems. In the face …
PDF, 988 Kb, Datei veröffentlicht: 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.
Auszug aus dem Dokument
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 …
PDF, 1.2 Mb, Datei veröffentlicht: Oct 1, 1988
This note examines a wide range of DC/DC converter applications. Single inductor, transformer, and switched-capacitor converter designs are shown. Special topics like low noise, high efficiency, low quiescent current, high voltage, and wide-input voltage range converters are covered. Appended sections explain some fundamental properties of different types of converters.
Auszug aus dem Dokument
Application Note 29
October 1988
Some Thoughts on DC/DC Converters
Jim Williams and Brian Huffman
INTRODUCTION
Many systems require that the primary source of DC power
be converted to other voltages. Battery driven circuitry is
an obvious candidate. The 6V or 12V cell in a laptop computer must be converted to different potentials needed for
memory, disc drives, display and operating logic. In theory,
AC line powered systems should not need DC/DC converters
because the implied power transformer can be equipped
with multiple secondaries. In practice, economics, noise
requirements, supply bus distribution problems and other
constraints often make DC/DC conversion preferable. A
common example is logic dominated, 5V powered systems
utilizing В±15V driven analog components.
The range of applications for DC/DC converters is large,
with many variations. Interest in converters is commensurately quite high. Increased use of single supply powered
systems, stiffening performance requirements and battery
operation have increased converter usage.
Historically, efficiency and size have received heavy emphasis. In fact, these parameters can be significant, but
often are of secondary importance. A possible reason
behind the continued and overwhelming attention to size …
PDF, 606 Kb, Datei veröffentlicht: Feb 1, 1989
Switching regulators are of universal interest. Linear Technology has made a major effort to address this topic. A catalog of circuits has been compiled so that a design engineer can swiftly determine which converter type is best. This catalog serves as a visual index to be browsed through for a specific or general interest.
Auszug aus dem Dokument
Application Note 30
February 1989
Switching Regulator Circuit Collection
John Seago
Switching regulators are of universal interest. Linear
Technology has made a major effort to address this topic.
A catalog of circuits has been compiled so that a design
engineer can swiftly determine which converter type is
best. This catalog serves as a visual index to be browsed
through for a specific or general interest. The catalog is organized so that converter topologies can
be easily found. There are 12 basic circuit categories:
Battery, Boost, Buck, Buck-Boost, Flyback, Forward, High
Voltage, Multioutput, Off Line, Preregulator, Switched
Capacitor and Telecom. Additional circuit information can
be located in the references listed in the index. The
reference works as follows, i.e., AN8, Page 2 = Application
Note 8, Page 2; LTC1044 DS = LTC1044 data sheet;
DN17 = Design Note 17. DRAWING INDEX
FIGURE TITLE FIGURE # PAGE REFERENCE/SOURCE Battery
2A Converter with 150ВµA Quiescent Current (6V to 12V)
200mA Output Converter (1.5V to 5V)
Up Converter (6V to 15V)
Regulated Up Converter (5V to 10V) …
PDF, 1.5 Mb, Datei veröffentlicht: Feb 2, 1989
Subtitled "Some Affable Analogs for Digital Devotees," discusses a number of analog circuits useful in predominantly digital systems. VPP generators for flash memories receive extensive treatment. Other examples include a current loop transmitter, dropout detectors, power management circuits, and clocks.
PDF, 818 Kb, Datei veröffentlicht: Mar 1, 1989
Presents circuit techniques permitting high efficiency to be obtained with linear regulation. Particular attention is given to the problem of maintaining high efficiency with widely varying inputs, outputs and loading. Appendix sections review component characteristics and measurement methods.
Auszug aus dem Dokument
Application Note 32
March 1989
High Efficiency Linear Regulators
Jim Williams
Introduction
Linear voltage regulators continue to enjoy widespread use
despite the increasing popularity of switching approaches.
Linear regulators are easily implemented, and have much
better noise and drift characteristics than switchers. Additionally, they do not radiate RF, function with standard
magnetics, are easily frequency compensated, and have
fast response. Their largest disadvantage is inefficiency.
Excess energy is dissipated as heat. This elegantly simplistic regulation mechanism pays dearly in terms of lost
power. Because of this, linear regulators are associated
with excessive dissipation, inefficiency, high operating
temperatures and large heat sinks. While linears cannot
compete with switchers in these areas they can achieve
significantly better results than generally supposed. New
components and some design techniques permit retention of linear regulator’s advantages while improving
efficiency.
One way towards improved efficiency is to minimize the
input-to-output voltage across the regulator. The smaller
this term is, the lower the power loss. The minimum input/
output voltage required to support regulation is referred …
PDF, 6.2 Mb, Datei veröffentlicht: Aug 1, 1989
Discusses the LT1074, an easily applied step-down regulator IC. Basic concepts and circuits are described along with more sophisticated applications. Six appended sections cover LT1074 circuitry detail, inductor and discrete component selection, current measuring techniques, efficiency considerations and other topics.
Auszug aus dem Dokument
Application Note 35
August 1989
Step-Down Switching Regulators
Jim Williams
lost in this voltage-to-current-to-magnetic п¬Ѓeld-to-current-to-charge-to-voltage conversion. In practice, the
circuit elements have losses, but step-down efficiency is
still higher than with inherently dissipative (e.g., voltage
divider) approaches. Figure 2 feedback controls the basic
circuit to regulate output voltage. In this case switch ontime (e.g., inductor charge time) is varied to maintain the
output against changes in input or loading.
REGULATED
OUTPUT IN PULSE
WIDTH
MODULATOR Figure 1 is a conceptual voltage step-down or “buck”
circuit. When the switch closes the input voltage appears
at the inductor. Current flowing through the inductor-capacitor combination builds over time. When the switch
IN OUT AN35 F01 Figure 1. Conceptual Voltage Step-Down (“Buck”) Circuit opens current flow ceases and the magnetic field around
the inductor collapses. Faraday teaches that the voltage
induced by the collapsing magnetic п¬Ѓeld is opposite to the
originally applied voltage. As such, the inductor’s left side
heads negative and is clamped by the diode. The capacitors accumulated charge has no discharge path, and a DC
potential appears at the output. This DC potential is lower
than the input because the inductor limits current during …
PDF, 1.7 Mb, Datei veröffentlicht: Jun 1, 1991
A wide variety of voltage reference circuits are detailed in this extensive guidebook of circuits. The detailed schematics cover simple and precision approaches at a variety of power levels. Included are 2 and 3 terminal devices in series and shunt modes for positive and negative polarities. Appended sections cover resistor and capacitor selection and trimming techniques.
PDF, 3.8 Mb, Datei veröffentlicht: Jun 1, 1990
Subtitled "Marrying Gain and Balance," this note covers signal conditioning circuits for various types of bridges. Included are transducer bridges, AC bridges, Wien bridge oscillators, Schottky bridges, and others. Special attention is given to amplifier selection criteria. Appended sections cover strain gauge transducers, understanding distortion measurements, and historical perspectives on bridge readout mechanisms and Wein bridge oscillators.
Auszug aus dem Dokument
Application Note 43
June 1990
Bridge Circuits
Marrying Gain and Balance
Jim Williams
Bridge circuits are among the most elemental and powerful
electrical tools. They are found in measurement, switching, oscillator and transducer circuits. Additionally, bridge
techniques are broadband, serving from DC to bandwidths
well into the GHz range. The electrical analog of the mechanical beam balance, they are also the progenitor of all
electrical differential techniques. and stability of the basic configuration. In particular, transducer manufacturers are quite adept at adapting the bridge
to their needs (see Appendix A, “Strain Gauge Bridges”).
Careful matching of the transducer’s mechanical characteristics to the bridge’s electrical response can provide a
trimmed, calibrated output. Similarly, circuit designers
have altered performance by adding active elements (e.g.,
amplifiers) to the bridge, excitation source or both. Resistance Bridges
Figure 1 shows a basic resistor bridge. The circuit is
usually credited to Charles Wheatstone, although S. H.
Christie, who demonstrated it in 1833, almost certainly
preceded him.1 If all resistor values are equal (or the two
sides ratios are equal) the differential voltage is zero. The
excitation voltage does not alter this, as it affects both
sides equally. When the bridge is operating off null, the
excitation’s magnitude sets output sensitivity. The bridge …
PDF, 1.2 Mb, Datei veröffentlicht: 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.
Auszug aus dem Dokument
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 …
PDF, 175 Kb, Datei veröffentlicht: Dec 1, 1984
6 applications utilizing thermally based circuits are detailed. Included are a 50MHz RMS to DC converter, and anemometer, a liquid flow meter and others. A general discussion of thermodynamic considerations involved in circuitry is also presented.
Auszug aus dem Dokument
Application Note 5
December 1984
Thermal Techniques in Measurement and Control Circuitry
Jim Williams
Designers spend much time combating thermal effects in
circuitry. The close relationship between temperature and
electronic devices is the source of more design headaches
than any other consideration. regulator’s output low, biasing Q1. As the heater warms,
the thermistor ’s value decreases. When its inputs finally
balance, A1 comes out of saturation and the LT3525A pulse
width modulates the heater via Q1, completing a feedback
path. A1 provides gain and the LT3523A furnishes high
efficiency. The 2kHz pulse width modulated heater power
is much faster than the thermal loop’s response and the
oven sees an even, continuous heat flow. In fact, instead of eliminating or compensating for thermal
parasitics in circuits, it is possible to utilize them. In particular, applying thermal techniques to measurement and
control circuits allows novel solutions to difficult problems.
The most obvious example is temperature control. Familiarity with thermal considerations in temperature control
loops permits less obvious, but very useful, thermallybased circuits to be built. The key to high performance control is matching the gain
bandwidth of A1 to the thermal feedback path. Theoretically, it is a simple matter to do this using conventional
servo-feedback techniques. Practically, the long time
constants and uncertain delays inherent in thermal systems
present a challenge. The unfortunate relationship between …
PDF, 213 Kb, Datei veröffentlicht: 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.
Auszug aus dem Dokument
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: …
PDF, 1.1 Mb, Datei veröffentlicht: Aug 1, 1994
This collection of circuits was worked out between June 1991 and July of 1994. Most were designed at customer request or are derivatives of such efforts. Types of circuits include power converters, transducer signal conditioners, amplifiers and signal generators. Specific circuits include low noise amplifiers, high power single cell DC/DC converters, portable high accuracy barometers, a 10mHz 1% accuracy RMS/DC converter, and random noise generators. Appended sections cover noise theory and present a historical perspective of wideband amplifiers.
Auszug aus dem Dokument
Application Note 61
August 1994
Practical Circuitry for Measurement and Control Problems
Circuits Designed for a Cruel and Unyielding World
Jim Williams
INTRODUCTION currents associated with the continuous operation of fixed
frequency designs. Gated oscillator regulators simply
self-clock at whatever frequency is required to maintain
the output voltage. Typically, loop oscillation frequency
ranges from a few hertz into the kilohertz region, depending upon the load. This collection of circuits was worked out between June
1991 and July of 1994. Most were designed at customer
request or are derivatives of such efforts. All represent
substantial effort and, as such, are disseminated here
for wider study and (hopefully) use.1 The examples are
roughly arranged in categories including power conversion, transducer signal conditioning, amplifiers and signal
generators. As always, reader comment and questions
concerning variants of the circuits shown may be addressed
directly to the author. In most cases this asynchronous, variable frequency operation does not create problems. Some systems, however, are
sensitive to this characteristic. Figure 1 slightly modifies
a gated oscillator type switching regulator by synchronizing its loop oscillation frequency to the systems clock. In
this fashion the oscillation frequency and its attendant
switching noise, albeit variable, become coherent with
system operation. Clock Synchronized Switching Regulator …
PDF, 297 Kb, Datei veröffentlicht: Feb 1, 1985
Analog-to-digital conversion circuits which directly digitize low level transducer outputs, without DC preamplification, are presented. Covered are circuits which operate with thermocouples, strain gauges, humidity sensors, level transducers and other sensors.
Auszug aus dem Dokument
Application Note 7
February 1985
Some Techniques for Direct Digitization of Transducer Outputs
Jim Williams
Almost all transducers produce low level signals. Normally,
high accuracy signal conditioning amplifiers are used to
boost these outputs to levels which can easily drive cables,
additional circuitry, or data converters. This practice raises
the signal processing range well above the error floor,
permitting high resolution over a wide dynamic range.
Some emerging trends in transducer-based systems are
causing the use of signal conditioning amplifiers to be
reevaluated. While these amplifiers will always be useful,
their utilization may not be as universal as it once was.
In particular, many industrial transducer-fed systems are
employing digital transmission of signals to eliminate
noise-induced inaccuracies in long cable runs. Additionally, the increasing digital content of systems, along with
pressures on board space and cost, make it desirable to
digitize transducer outputs as far forward in the signal chain
as possible. These trends point toward direct digitization
of transducer outputs—a difficult task.
Classical A/D conversion techniques emphasize high level
input ranges. This allows LSB step size to be as large …
PDF, 882 Kb, Datei veröffentlicht: 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.
Auszug aus dem Dokument
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 …
PDF, 508 Kb, Datei veröffentlicht: Mar 1, 1999
This publication includes designs for data converters and signal conditioners, transducer circuits, crystal oscillators and power converters. Wideband and micropower circuitry receive special attention. Tutorials on micropower design techniques and parasitic effects of test equipment are included.
Auszug aus dem Dokument
Application Note 75
March 1999
Circuitry for Signal Conditioning and
Power Conversion
Designs From a Once Lazy Sabbatical
Jim Williams
Introduction
Linear Technology has a sabbatical program. Every five
years employees are granted sabbatical leave, which may
last up to six weeks. You have 18 months from each five
year employment anniversary to take the leave. Sabbatical
is fully company paid and has no restrictions. The time is
yours to do with as you please.
People exercise all degrees of freedom with their sabbaticals. They go sailing, they go to South Sea islands, they ski
some mountain nobody ever heard of, they trek in Nepal.
Houses get fixed, cars restored and children played with.
For my third sabbatical I resolved to do absolutely nothing.
For the first time in my life I was really tired, and I knew it.
A six week rest sounded just fine. I’d walk the dog and
spend time with my wife and son. That’s it. No transistors,
no resistors, no op amps and, above all, no writing. I was
so written out the thought of picking up a pencil produced
an instant headache. …
PDF, 708 Kb, Datei veröffentlicht: May 1, 1985
A variety of approaches for power conditioning batteries is given. Switching and linear regulators and converters are shown, with attention to efficiency and low power operation. 14 circuits are presented with performance data.
PDF, 172 Kb, Datei veröffentlicht: Nov 1, 1999
Just how do bandgaps and buried Zeners stack up against Weston cells? Did you know your circuit board may induce more drift in a reference than time and temperature? Learn the answers to these and other commonly asked reference questions ranging from burn-in recommendations to ΔVBE generation in this Application Note.
Auszug aus dem Dokument
Application Note 82
November 1999
Understanding and Applying Voltage References 30
2 4 20
8 3
10 –20
16
32 4
–30 5 Today’s IC reference technology is divided along two
lines: bandgap references, which balance the temperature coefficient of a forward-biased diode junction against
that of a ∆VBE (see Appendix B); and buried Zeners (see
Appendix A), which use subsurface breakdown to achieve
outstanding long-term stability and low noise. With few
exceptions, both reference types use additional on-chip
circuitry to further minimize temperature drift and trim
output voltage to an exact value. Bandgap references are
generally used in systems of up to 12 bits; buried Zeners
take over from there in higher accuracy systems.
, LTC and LT are registered trademarks of Linear Technology Corporation. –1 5
3
2 64 6
1 –40 As with other specialized electronic fields, the field of
monolithic references has its own vocabulary. We’ve …
PDF, 625 Kb, Datei veröffentlicht: Aug 5, 1986
A discussion of circuit, layout and construction considerations for low level DC circuits includes error analysis of solder, wire and connector junctions. Applications include sub-microvolt instrumentation and isolation amplifiers, stabilized buffers and comparators and precision data converters.
Auszug aus dem Dokument
Application Note 9
August 1986
Application Considerations and Circuits for a New
Chopper-Stabilized Op Amp
Jim Williams
A great deal of progress has been made in op amp DC
characteristics. Carefully executed designs currently available provide sub-microvolt VOS О”T drift, low bias currents
and open-loop gains exceeding one million. Considerable
design and processing advances were required to achieve
these specifications. Because of this, it is interesting to
note that amplifiers with even better DC specification
were available in 1963 (Philbrick Researches Model
SP656). Although these modular amplifiers were large
and expensive (≈3" × 2" × 1.5" at $195.00 1963 dollars)
by modern standards, their DC performance anticipated
today’s best monolithic amplifiers while using relatively
primitive components. This was accomplished by employing chopper-stabilization techniques (see Box “Choppers,
Chopper-Stabilization and the LTC®1052”) instead of the
more common DC-differential stage approach.
The chopper-stabilized approach, developed by E. A.
Goldberg in 1948, uses the amplifier’s input to amplitude
modulate an AC carrier. This carrier, amplified and synchronously demodulated back to DC, furnishes the amplifier’s PARAMETER
EOS – 25В°C …