SNOS611F July   1999  – March 2025 LMC6041 , LMC6042 , LMC6044

PRODUCTION DATA  

  1.   1
  2. 1Features
  3. 2Applications
  4. 3Description
  5. 4Pin Configuration and Functions
  6. 5Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information: LMC6041
    5. 5.5 Thermal Information: LMC6042
    6. 5.6 Thermal Information: LMC6044
    7. 5.7 Electrical Characteristics
    8. 5.8 Typical Characteristics
  7. 6Application and Implementation
    1. 6.1 Application Information
      1. 6.1.1 Amplifier Topology
      2. 6.1.2 Compensating For Input Capacitance
      3. 6.1.3 Capacitive-Load Tolerance
    2. 6.2 Typical Applications
      1. 6.2.1 Instrumentation Amplifiers
      2. 6.2.2 Low-Leakage Sample and Hold
      3. 6.2.3 Square-Wave Generator
      4. 6.2.4 AC Coupled Power Amplifier
    3. 6.3 Layout
      1. 6.3.1 Layout Guidelines
        1. 6.3.1.1 Printed-Circuit-Board Layout for High-Impedance Work
      2. 6.3.2 Layout Examples
  8. 7Device and Documentation Support
    1. 7.1 Receiving Notification of Documentation Updates
    2. 7.2 Support Resources
    3.     Trademarks
    4. 7.3 Electrostatic Discharge Caution
    5. 7.4 Glossary
  9. 8Revision History
  10. 9Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • D|8
  • P|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information

6.2.1 Instrumentation Amplifiers

The extremely high input impedance and low power consumption of the LMC604x make these op amps an excellent choice for applications that require battery-powered instrumentation amplifiers. Examples of these types of applications are portable pH probes, analytic medical instruments, magnetic field detectors, gas detectors, and silicon-based pressure transducers.

The circuit in Figure 6-4 is recommended for applications where the common-mode input range is relatively low and the differential gain is in the range of 10 to 1000. This two op-amp instrumentation amplifier features an independent adjustment of the gain and common-mode rejection trim, and a total quiescent supply current of less than 20μA. To maintain ultra-high input impedance, use ground rings and consider printed circuit board (PCB) layout an important part of the overall system design (see Printed Circuit Board Layout for High Impedance Work). Figure 6-4 shows that the input voltages are represented as a common-mode input VCM plus a differential input VD.

Rejection of the common-mode component of the input is accomplished by making the ratio of R1/R2 equal to R3/R4. So that:

Equation 3. R 3 R 4 = R 2 R 1

The gain equation of the instrumentation amplifier is given by:

Equation 4. V O U T = R 4 R 3 1 + R 3 R 4 + R 2 + R 3 R 0

A suggested design guideline is to minimize the difference of the value between R1 through R4. Minimizing often results in improved resistor temperature coefficient, amplifier gain, and CMRR over temperature. If RN = R1 = R2 = R3 = R4 then the gain equation is simplified as:

Equation 5. V O U T = 2 V D 1 + R N R 0

As a result of the zero-in, zero-out performance of the LMC604x, and output swing rail-to-rail, the dynamic range is only limited to the input common-mode range of 0V to VS − 2.3V, the worst case at room temperature. This feature of the LMC604x makes these op amps an excellent choice for low-power instrumentation systems.

Figure 6-5 shows a complete instrumentation amplifier designed for a gain of 100. Provisions are made for the low-sensitivity trimming of CMRR and gain.

LMC6041 LMC6042 LMC6044 Two-Op-Amp Instrumentation AmplifierFigure 6-4 Two-Op-Amp Instrumentation Amplifier
LMC6041 LMC6042 LMC6044 Instrumentation AmplifierFigure 6-6 Instrumentation Amplifier
LMC6041 LMC6042 LMC6044 Low-Power, Two-Op-Amp Instrumentation AmplifierFigure 6-5 Low-Power, Two-Op-Amp
Instrumentation Amplifier