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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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  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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• Signal Conditioning > Amplifiers > Operational Amplifiers (Op Amps) > Low Bias Current Amplifiers (Ib < 100pA) | High Voltage Amplifiers (>12V) | JFET Input Amplifiers