LMC6482QML Datasheet, PDF (21/28 Pages) Texas Instruments – CMOS Dual Rail-To-Rail Input and Output Operational Amplifier

10.0 INSTRUMENTATION CIRCUITS
The LMC6482 has the high input impedance, large common-
mode range and high CMRR needed for designing instru-
mentation circuits. Instrumentation circuits designed with the
LMC6482 can reject a larger range of common-mode signals
than most in-amps. This makes instrumentation circuits de-
signed with the LMC6482 an excellent choice of noisy or
industrial environments. Other applications that benefit from
these features include analytic medical instruments, magnetic
field detectors, gas detectors, and silicon-based transducers.
A small valued potentiometer is used in series with R_g to set
the differential gain of the 3 op-amp instrumentation circuit in
Figure 15. This combination is used instead of one large val-
ued potentiometer to increase gain trim accuracy and reduce
error due to vibration.
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FIGURE 15. Low Power 3 Op-Amp Instrumentation Amplifier
A 2 op-amp instrumentation amplifier designed for a gain of
100 is shown in Figure 16. Low sensitivity trimming is made
for offset voltage, CMRR and gain. Low cost and low power
consumption are the main advantages of this two op-amp cir-
cuit.
Higher frequency and larger common-mode range applica-
tions are best facilitated by a three op-amp instrumentation
amplifier.
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FIGURE 16. Low-Power Two-Op-Amp Instrumentation Amplifier
11.0 SPICE MACROMODEL
A spice macromodel is available for the LMC6482. This model
includes accurate simulation of:
• Input common-mode voltage range
• Frequency and transient response
• GBW dependence on loading conditions
• Quiescent and dynamic supply current
• Output swing dependence on loading conditions
and many more characteristics as listed on the macromodel
disk.
Contact your local National Semiconductor sales office to ob-
tain an operational amplifier spice model library disk.
www.national.com
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