SNOSAW6E January 2008  – December 2014 LMP7721

PRODUCTION DATA. 

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1Absolute Maximum Ratings
    2. 6.2ESD Ratings
    3. 6.3Recommended Operating Conditions
    4. 6.4Thermal Information
    5. 6.5Electrical Characteristics: 2.5 V
    6. 6.6Electrical Characteristics: 5 V
    7. 6.7Typical Characteristics
  7. Detailed Description
    1. 7.1Overview
    2. 7.2Functional Block Diagram
    3. 7.3Feature Description
      1. 7.3.1Ultra-Low Input Bias Current
      2. 7.3.2Wide Bandwidth at Low-Supply Current
      3. 7.3.3Low Input Referred Noise
      4. 7.3.4Low-Supply Voltage
      5. 7.3.5Rail-to-Rail Output and Ground Sensing
      6. 7.3.6Unique Pinout
      7. 7.3.7Input Protection
    4. 7.4Device Functional Modes
      1. 7.4.1Compensating Input Capacitance
  8. Application and Implementation
    1. 8.1Application Information
      1. 8.1.1Using a Guard
      2. 8.1.2Use Triaxial Cable
      3. 8.1.3Properly Clean the Assembly
    2. 8.2Typical Application
      1. 8.2.1Design Requirements
      2. 8.2.2Detailed Design Procedure
      3. 8.2.3Application Curve
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1Layout Guidelines
    2. 10.2Layout Example
  11. 11Device and Documentation Support
    1. 11.1Device Support
      1. 11.1.1Development Support
    2. 11.2Documentation Support
      1. 11.2.1Related Documentation
    3. 11.3Trademarks
    4. 11.4Electrostatic Discharge Caution
    5. 11.5Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Orderable Information

1 Features

  • Unless Otherwise Noted, Typical Values at TA = 25°C, VS = 5 V.
  • Input Bias Current (VCM = 1 V)
    • Maximum at 25°C ±20 fA
    • Maximum at 85°C ±900 fA
  • Offset Voltage ±26 µV
  • Offset Voltage Drift −1.5 μV/°C
  • DC Open-Loop Gain 120 dB
  • DC CMRR 100 dB
  • Input Voltage Noise (at f = 1 kHz) 6.5 nV/√Hz
  • THD 0.0007%
  • Supply Current 1.3 mA
  • GBW 17 MHz
  • Slew Rate (Falling Edge) 12.76 V/μs
  • Supply Voltage 1.8 V to 5.5 V
  • Operating Temperature Range −40°C to 125°C
  • 8-Pin SOIC

2 Applications

  • Photodiode Amplifier
  • High Impedance Sensor Amplifier
  • Ion Chamber Amplifier
  • Electrometer Amplifier
  • pH Electrode Amplifier
  • Transimpedance Amplifier

Ultra-Low Input Bias Current

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3 Description

The LMP7721 is the industry’s lowest specified input bias current precision amplifier. The ultra-low input bias current is 3 fA, with a specified limit of ±20 fA at 25°C and ±900 fA at 85°C. This is achieved with the latest patent-pending technology of input bias current cancellation amplifier circuitry. This technology also maintains the ultra-low input bias current over the entire input common-mode voltage range of the amplifier.

Other outstanding features, such as low voltage noise (6.5 nV/√Hz), low DC-offset voltage (±150 µV maximum at 25°C) and low-offset voltage temperature coefficient (−1.5 µV/°C), improve system sensitivity and accuracy in high-precision applications. With a supply voltage range of 1.8 V to 5.5 V, the LMP7721 is the ideal choice for battery-operated, portable applications. The LMP7721 is part of the LMP™ precision amplifier family.

As part of Texas Instruments' PowerWise™ products, the LMP7721 provides the remarkably wide-gain bandwidth product (GBW) of 17 MHz while consuming only 1.3 mA of current. This wide GBW along with the high open-loop gain of 120 dB enables accurate signal conditioning. With these specifications, the LMP7721 has the performance to excel in a wide variety of applications such as electrochemical cell amplifiers and sensor interface circuits.

The LMP7721 is offered in an 8-pin SOIC package with a special pinout that isolates the amplifier’s input from the power supply and output pins. With proper board layout techniques, the unique pinout of the LMP7721 will prevent PCB leakage current from reaching the input pins. Thus system error will be further reduced.

Device Information(1)

PART NUMBERPACKAGEBODY SIZE (NOM)
LMP7721SOIC (8)4.90 mm × 3.90 mm
  1. For all available packages, see the orderable addendum at the end of the datasheet.