LMC6041

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SNOS610E – DECEMBER 1994 – REVISED MARCH 2013

(Input pins are lifted out of PC board and soldered directly to components. All other pins connected to PC board.)

Figure 35. Air Wiring

Typical Single-Supply Applications

The extremely high input impedance, and low power consumption, of the LMC6041 make it ideal for applications

that require battery-powered instrumentation amplifiers. Examples of these type of applications are hand-held pH

probes, analytic medical instruments, magnetic field detectors, gas detectors, and silicon based pressure

transducers.

Figure 36. Two Op-Amp Instrumentation Amplifier

The circuit in Figure 36 is recommended for applications where the common-mode input range is relatively low

and the differential gain will be 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 28

μA. To maintain ultra-high input impedance, it is advisable to use ground rings and consider PC board

layout an important part of the overall system design (see Printed-Circuit-Board Layout for High Impedance

Rejection of the common-mode component of the input is accomplished by making the ratio of R1/R2 equal to

R3/R4. So that where,

(3)

A suggested design guideline is to minimize the difference of value between R1 through R4. This will often result

in improved resistor tempco, amplifier gain, and CMRR over temperature. If RN = R1 = R2 = R3 = R4 then the

gain equation can be simplified:

(4)

Due to the “zero-in, zero-out” performance of the LMC6041, and output swing rail-rail, the dynamic range is only

LMC6041 makes it an ideal choice for low-power instrumentation systems.

Copyright © 1994–2013, Texas Instruments Incorporated

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