SNOSAI7K September   2005  – May 2016 LMV651 , LMV652 , LMV654

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 3-V DC Electrical Characteristics
    6. 6.6 5-V DC Electrical Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Low Voltage and Low Power Operation
      2. 7.3.2 Wide Bandwidth
      3. 7.3.3 Low Input Referred Noise
      4. 7.3.4 Ground Sensing and Rail-to-Rail Output
      5. 7.3.5 Small Size
    4. 7.4 Device Functional Modes
      1. 7.4.1 Stability and Capacitive Loading
      2. 7.4.2 In The Loop Compensation
      3. 7.4.3 Compensation By External Resistor
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 High Gain, Low Power Inverting Amplifiers
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curve
      2. 8.2.2 High Gain, Low Power Noninverting Amplifiers
      3. 8.2.3 Active Filters
    3. 8.3 Dos and Don'ts
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

8.1 Application Information

With a low supply current, low power operation, and low harmonic distortion, the LMV65x devices are ideal for wide-bandwidth, high gain amplification.

8.2 Typical Applications

8.2.1 High Gain, Low Power Inverting Amplifiers

LMV651 LMV652 LMV654 20123861.gif Figure 37. High Gain Inverting Amplifier

8.2.1.1 Design Requirements

The wide unity-gain bandwidth allows these parts to provide large gain over a wide frequency range, while driving loads as low as 2 kΩ with less than 0.003% distortion.

8.2.1.2 Detailed Design Procedure

Figure 37 is an inverting amplifier, with a 100-kΩ feedback resistor, R2, and a 1-kΩ input resistor, R1, and provides a gain of −100. With the LMV65x, these circuits can provide gain of −100 with a −3-dB bandwidth of 120 kHz, for a quiescent current as low as 116 μA. Coupling capacitors CC1 and CC2 can be added to isolate the circuit from DC voltages, while RB1 and RB2 provide DC biasing. A feedback capacitor CF can also be added to improve compensation.

8.2.1.3 Application Curve

LMV651 LMV652 LMV654 C001_.png Figure 38. High Gain Inverting Amplifier Results

8.2.2 High Gain, Low Power Noninverting Amplifiers

With a low supply current, low power operation, and low harmonic distortion, the LMV65x devices are ideal for wide-bandwidth, high gain amplification. The wide unity-gain bandwidth allows these parts to provide large gain over a wide frequency range, while driving loads as low as 2 kΩ with less than 0.003% distortion. Figure 39 is a noninverting amplifier with a gain of 1001, can provide that gain with a −3-dB bandwidth of 12 kHz, for a similar low quiescent power dissipation. With the LMV65x, these circuits can provide gain of −100 with a −3-dB bandwidth of 120 kHz, for a quiescent current as low as 116 μA. Coupling capacitors CC1 and CC2 can be added to isolate the circuit from DC voltages, while RB1 and RB2 provide DC biasing. A feedback capacitor CF can also be added to improve compensation.

LMV651 LMV652 LMV654 20123862.gif Figure 39. High Gain Noninverting Amplifier

8.2.3 Active Filters

With a wide unity-gain bandwidth of 12 MHz, low input-referred noise density, and a low power supply current, the LMV65x devices are well suited for low-power filtering applications. Active filter topologies, like the Sallen-Key low-pass filter shown in Figure 40, are very versatile, and can be used to design a wide variety of filters (Chebyshev, Butterworth, or Bessel). The Sallen-Key topology, in particular, can be used to attain a wide range of Q, by using positive feedback to reject the undesired frequency range.

In the circuit shown in Figure 40, the two capacitors appear as open circuits at lower frequencies and the signal is simply buffered to the output. At high frequencies the capacitors appear as short circuits and the signal is shunted to ground by one of the capacitors before it can be amplified. Near the cutoff frequency, where the impedance of the capacitances is on the same order as Rg and Rf, positive feedback through the other capacitor allows the circuit to attain the desired Q. The ratio of the two resistors, m2, provides a knob to control the value of Q obtained.

LMV651 LMV652 LMV654 20123820.gif Figure 40. Sallen-Key Low-Pass Filter

8.3 Dos and Don'ts

Do properly bypass the power supplies.

Do add series resistence to the output when driving capacitive loads, particularly cables, Muxes, and ADC inputs.

Do add series current limiting resistors and external Schottky clamp diodes if input voltage is expected to exceed the supplies. Limit the current to 1 mA or less (1 kΩ per volt).