PDF, 387 Kb, File published: 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.
Extract from the document
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, 421 Kb, File published: Aug 1, 1985
This note describes some of the unique IC design techniques incorporated into a fast, monolithic power buffer, the LT1010. Also, some application ideas are described such as capacitive load driving, boosting fast op amp output current and power supply circuits.
Extract from the document
Application Note 16
August 1985
Unique IC Buffer Enhances Op Amp Designs,
Tames Fast Amplifiers
Robert J. Widlar
Abstract: A unity gain IC power buffer that uses NPN
output transistors while avoiding the usual problems of
quasi-complementary designs is described. Free of parasitic oscillations and stable with large capacitive loads, the
buffer has a 20MHz bandwidth, a 100V/Ојs slew and can
drive В±10V into a 75О© load. Standby current is 5mA. A
number of applications using the buffer are detailed, and
it is shown that a buffer has many uses beyond driving
a heavy load.
Introduction
An output buffer can do much more than increase the
output swing of an op amp. It can also eliminate ringing
with large capacitive loads. Fast buffers can improve the
performance of high speed followers, integrators and
sample/hold circuits, while at the same time making them
much easier to work with.
Interest in buffers has been low because a reasonably
priced, high performance, general purpose part has not
been available. Ideally, a buffer should be fast, have no …
PDF, 2.5 Mb, File published: Mar 1, 1986
This note presents output state circuits which provide power gain for monolithic amplifiers. The circuits feature voltage gain, current gain, or both. Eleven designs are shown, and performance is summarized. A generalized method for frequency compensation appears in a separate section.
Extract from the document
Application Note 18
March 1986
Power Gain Stages for Monolithic Amplifiers
Jim Williams
Most monolithic amplifiers cannot supply more than a few
hundred milliwatts of output power. Standard IC processing
techniques set device supply levels at 36V, limiting available output swing. Additionally, supplying currents beyond
tens of milliamperes requires large output transistors and
causes undesirable IC power dissipation.
Many applications, however, require greater output power
than most monolithic amplifiers will deliver. When voltage
or current gain (or both) is needed, a separate output
stage is necessary. The power gain stage, sometimes
called a “booster”, is usually placed within the monolithic
amplifier’s feedback loop, preserving the IC’s low drift and
stable gain characteristics. 150mA Output Stage
Figure 1a shows the LTВ®1010 monolithic 150mA current
booster placed within the feedback loop of a fast FET
amplifier. At lower frequencies, the buffer is within the
feedback loop so that its offset voltage and gain errors
are negligible. At higher frequencies, feedback is through
Cf, so that phase shift from the load capacitance acting
against the buffer output resistance does not cause loop …
PDF, 330 Kb, File published: Jul 1, 1986
Applications often require an amplifier that has extremely high performance in several areas. For example, high speed and DC precision are often needed. If a single device cannot simultaneously achieve the desired characteristics, a composite amplifier made up of two (or more) devices can be configured to do the job. AN21 shows examples of composite approaches in designs combining speed, precision, low noise and high power.
Extract from the document
Application Note 21
July 1986
Composite Amplifiers
Jim Williams
Amplifier design, regardless of the technology utilized, is
a study in compromise. Device limitations make it difficult
for a particular amplifier to achieve optimal speed, drift,
bias current, noise and power output specifications. As
such, various amplifier families emphasizing one or more
of these areas have evolved. Some amplifiers are very good
attempts at doing everything well, but the best achievable
performance п¬Ѓgures are limited to dedicated designs. designed with little attention to DC biasing considerations
if a separate stabilizing stage is employed.
Figure 1 shows a composite made up of an LTВ®1012 low drift
device and an LT1022 high speed amplifier. The overall circuit is a unity-gain inverter, with the summing node located
at the junction of three 10k resistors. The LT1012 monitors
this summing node, compares it to ground and drives the
LT1022’s positive input, completing a DC stabilizing loop
around the LT1022. The 10k-300pF time constant at the
LT1012 limits its response to low frequency signals. The
LT1022 handles high frequency inputs while the LT1012
stabilizes the DC operating point. The 4.7k-220О© divider
at the LT1022 prevents excessive input overdrive during …
PDF, 1.5 Mb, File published: 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, 1.0 Mb, File published: Sep 23, 1984
The LT1010 150mA power buffer is described in a number of useful applications such as boosted op amp, a feed-forward, wideband DC stabilized buffer, a video line driver amplifier, a fast sample-hold with hold step compensation, an overload protected motor speed controller, and a piezoelectric fan servo.
Extract from the document
Application Note 4
September 1984
Applications for a New Power Buffer
Jim Williams
A frequent requirement in systems involves driving
analog signals into non-linear or reactive loads. Cables,
transformers, actuators, motors and sample-hold circuits
are examples where the ability to drive difficult loads is
required. Although several power buffer amplifiers are
available, none have been optimized for driving difficult
loads. The LTВ®1010 can isolate and drive almost any
reactive load. It also offers current limiting and thermal
overload protection which protect the device against output
fault conditions. The combination of good speed, output
protection, and reactive load driving capability (see box
section, “The LT1010 at a Glance”) make the device useful
in a variety of practical situations. Buffered Output Line Driver
Figure 1 shows the LT1010 placed within the feedback
loop of an operational amplifier. At lower frequencies, the
buffer is within the feedback loop and its offset voltage and
gain error are negligible. At higher frequencies, feedback
is through CF so that phase shift from load capacitance
acting against the buffer’s output resistance does not …
PDF, 3.8 Mb, File published: 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.
Extract from the document
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, 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.
Extract from the document
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, 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.
Extract from the document
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 …
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 …
PDF, 172 Kb, File published: 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.
Extract from the document
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, 540 Kb, File published: Jan 1, 2001
This publication details a true 1ppm D-to-A converter. Total DC error of this processor corrected DAC remains within 1ppm from 18-32°C, including reference drift. DAC error exclusive of reference drift is substantially better. Construction details and performance verification techniques are included, along with a complete software listing.
Extract from the document
Application Note 86
January 2001
A Standards Lab Grade 20-Bit DAC with 0.1ppm/В°C Drift
The Dedicated Art of Digitizing One Part Per Million
Jim Williams
J. Brubaker
P. Copley
J. Guerrero
F. Oprescu INTRODUCTION
Significant progress in high precision, instrumentation
grade D-to-A conversion has recently occurred. Ten years
ago 12-bit D-to-A converters (DACs) were considered
premium devices. Today, 16-bit DACs are available and
increasingly common in system design. These are true
precision devices with less than 1LSB linearity error and
1ppm/В°C drift.1 Nonetheless, there are DAC applications
that require even higher performance. Automatic test
equipment, instruments, calibration apparatus, laser trimmers, medical electronics and other applications often
require DAC accuracy beyond 16 bits. 18-bit DACs have
been produced in circuit assembly form, although they are
expensive and require frequent calibration. 20 and even
23+ (0.1ppm!) bit DACs are represented by manually
switched Kelvin-Varley dividers. These devices, although …
PDF, 625 Kb, File published: 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.
Extract from the document
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 …
